idnits 2.17.00 (12 Aug 2021) /tmp/idnits16683/draft-ietf-extra-imap4rev2-06.txt: Checking boilerplate required by RFC 5378 and the IETF Trust (see https://trustee.ietf.org/license-info): ---------------------------------------------------------------------------- No issues found here. Checking nits according to https://www.ietf.org/id-info/1id-guidelines.txt: ---------------------------------------------------------------------------- No issues found here. Checking nits according to https://www.ietf.org/id-info/checklist : ---------------------------------------------------------------------------- ** The document seems to lack an Introduction section. ** There are 13 instances of too long lines in the document, the longest one being 9 characters in excess of 72. -- The draft header indicates that this document obsoletes RFC3501, but the abstract doesn't seem to mention this, which it should. Miscellaneous warnings: ---------------------------------------------------------------------------- == The copyright year in the IETF Trust and authors Copyright Line does not match the current year == The document seems to contain a disclaimer for pre-RFC5378 work, but was first submitted on or after 10 November 2008. The disclaimer is usually necessary only for documents that revise or obsolete older RFCs, and that take significant amounts of text from those RFCs. If you can contact all authors of the source material and they are willing to grant the BCP78 rights to the IETF Trust, you can and should remove the disclaimer. Otherwise, the disclaimer is needed and you can ignore this comment. (See the Legal Provisions document at https://trustee.ietf.org/license-info for more information.) -- The document date (October 27, 2019) is 936 days in the past. Is this intentional? -- Found something which looks like a code comment -- if you have code sections in the document, please surround them with '' and '' lines. Checking references for intended status: Proposed Standard ---------------------------------------------------------------------------- (See RFCs 3967 and 4897 for information about using normative references to lower-maturity documents in RFCs) == Missing Reference: 'IMAP2' is mentioned on line 6257, but not defined == Missing Reference: 'IMAP-OBSOLETE' is mentioned on line 6252, but not defined == Missing Reference: 'IMAP-COMPAT' is mentioned on line 6242, but not defined == Missing Reference: 'IMAP-HISTORICAL' is mentioned on line 6247, but not defined == Missing Reference: 'RFC-822' is mentioned on line 6261, but not defined ** Obsolete undefined reference: RFC 822 (Obsoleted by RFC 2822) == Missing Reference: 'HEADER' is mentioned on line 5195, but not defined == Missing Reference: 'IMAP-DISC' is mentioned on line 6199, but not defined == Missing Reference: 'SMTP' is mentioned on line 6220, but not defined == Missing Reference: 'RFC7888' is mentioned on line 6195, but not defined -- Looks like a reference, but probably isn't: '1' on line 836 == Missing Reference: 'IMAP-URL' is mentioned on line 6234, but not defined == Missing Reference: 'UIDVALIDITY 3857529045' is mentioned on line 5178, but not defined == Missing Reference: 'UIDNEXT 4392' is mentioned on line 1633, but not defined == Missing Reference: 'RFC5258' is mentioned on line 6181, but not defined == Missing Reference: 'RFC2193' is mentioned on line 6186, but not defined == Missing Reference: 'RFC3348' is mentioned on line 6190, but not defined ** Obsolete undefined reference: RFC 3348 (Obsoleted by RFC 5258) == Missing Reference: 'UIDNEXT 2' is mentioned on line 3066, but not defined == Missing Reference: 'UIDVALIDITY 1' is mentioned on line 3137, but not defined == Missing Reference: 'IMAP-I18N' is mentioned on line 6204, but not defined == Missing Reference: 'TEXT' is mentioned on line 5132, but not defined == Missing Reference: 'UID' is mentioned on line 3827, but not defined == Missing Reference: 'RFC4314' is mentioned on line 6227, but not defined == Missing Reference: 'RFC2087' is mentioned on line 6231, but not defined ** Obsolete undefined reference: RFC 2087 (Obsoleted by RFC 9208) == Missing Reference: 'READ-WRITE' is mentioned on line 5179, but not defined == Missing Reference: 'RFC4422' is mentioned on line 5494, but not defined == Missing Reference: 'Namespace-Response-Extensions' is mentioned on line 5589, but not defined == Missing Reference: 'IMAP-TLS' is mentioned on line 6269, but not defined == Missing Reference: 'IMAP-MODEL' is mentioned on line 6210, but not defined == Missing Reference: 'IMAP-UTF-8' is mentioned on line 6287, but not defined == Missing Reference: 'RFC3516' is mentioned on line 6373, but not defined == Missing Reference: 'RFC-821' is mentioned on line 6265, but not defined ** Obsolete undefined reference: RFC 821 (Obsoleted by RFC 2821) ** Obsolete normative reference: RFC 5246 (ref. 'TLS') (Obsoleted by RFC 8446) ** Downref: Normative reference to an Informational RFC: RFC 2152 (ref. 'UTF-7') ** Downref: Normative reference to an Informational RFC: RFC 2683 (ref. 'IMAP-IMPLEMENTATION') ** Downref: Normative reference to an Informational RFC: RFC 2180 (ref. 'IMAP-MULTIACCESS') Summary: 10 errors (**), 0 flaws (~~), 32 warnings (==), 4 comments (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Network Working Group A. Melnikov, Ed. 3 Internet-Draft Isode Ltd 4 Obsoletes: 3501 (if approved) B. Leiba, Ed. 5 Intended status: Standards Track Huawei Technologies 6 Expires: April 29, 2020 October 27, 2019 8 INTERNET MESSAGE ACCESS PROTOCOL - VERSION 4rev2 9 draft-ietf-extra-imap4rev2-06 11 Abstract 13 The Internet Message Access Protocol, Version 4rev2 (IMAP4rev2) 14 allows a client to access and manipulate electronic mail messages on 15 a server. IMAP4rev2 permits manipulation of mailboxes (remote 16 message folders) in a way that is functionally equivalent to local 17 folders. IMAP4rev2 also provides the capability for an offline 18 client to resynchronize with the server. 20 IMAP4rev2 includes operations for creating, deleting, and renaming 21 mailboxes, checking for new messages, permanently removing messages, 22 setting and clearing flags, RFC 5322, RFC 2045 and RFC 2231 parsing, 23 searching, and selective fetching of message attributes, texts, and 24 portions thereof. Messages in IMAP4rev2 are accessed by the use of 25 numbers. These numbers are either message sequence numbers or unique 26 identifiers. 28 IMAP4rev2 does not specify a means of posting mail; this function is 29 handled by a mail submission protocol such as RFC 6409. 31 Status of This Memo 33 This Internet-Draft is submitted in full conformance with the 34 provisions of BCP 78 and BCP 79. 36 Internet-Drafts are working documents of the Internet Engineering 37 Task Force (IETF). Note that other groups may also distribute 38 working documents as Internet-Drafts. The list of current Internet- 39 Drafts is at https://datatracker.ietf.org/drafts/current/. 41 Internet-Drafts are draft documents valid for a maximum of six months 42 and may be updated, replaced, or obsoleted by other documents at any 43 time. It is inappropriate to use Internet-Drafts as reference 44 material or to cite them other than as "work in progress." 46 This Internet-Draft will expire on April 29, 2020. 48 Copyright Notice 50 Copyright (c) 2019 IETF Trust and the persons identified as the 51 document authors. All rights reserved. 53 This document is subject to BCP 78 and the IETF Trust's Legal 54 Provisions Relating to IETF Documents 55 (https://trustee.ietf.org/license-info) in effect on the date of 56 publication of this document. Please review these documents 57 carefully, as they describe your rights and restrictions with respect 58 to this document. Code Components extracted from this document must 59 include Simplified BSD License text as described in Section 4.e of 60 the Trust Legal Provisions and are provided without warranty as 61 described in the Simplified BSD License. 63 This document may contain material from IETF Documents or IETF 64 Contributions published or made publicly available before November 65 10, 2008. The person(s) controlling the copyright in some of this 66 material may not have granted the IETF Trust the right to allow 67 modifications of such material outside the IETF Standards Process. 68 Without obtaining an adequate license from the person(s) controlling 69 the copyright in such materials, this document may not be modified 70 outside the IETF Standards Process, and derivative works of it may 71 not be created outside the IETF Standards Process, except to format 72 it for publication as an RFC or to translate it into languages other 73 than English. 75 Table of Contents 77 1. How to Read This Document . . . . . . . . . . . . . . . . . . 5 78 1.1. Organization of This Document . . . . . . . . . . . . . . 5 79 1.2. Conventions Used in This Document . . . . . . . . . . . . 5 80 1.3. Special Notes to Implementors . . . . . . . . . . . . . . 6 81 2. Protocol Overview . . . . . . . . . . . . . . . . . . . . . . 7 82 2.1. Link Level . . . . . . . . . . . . . . . . . . . . . . . 7 83 2.2. Commands and Responses . . . . . . . . . . . . . . . . . 7 84 2.2.1. Client Protocol Sender and Server Protocol Receiver . 7 85 2.2.2. Server Protocol Sender and Client Protocol Receiver . 8 86 2.3. Message Attributes . . . . . . . . . . . . . . . . . . . 9 87 2.3.1. Message Numbers . . . . . . . . . . . . . . . . . . . 9 88 2.3.2. Flags Message Attribute . . . . . . . . . . . . . . . 11 89 2.3.3. Internal Date Message Attribute . . . . . . . . . . . 12 90 2.3.4. [RFC-5322] Size Message Attribute . . . . . . . . . . 13 91 2.3.5. Envelope Structure Message Attribute . . . . . . . . 13 92 2.3.6. Body Structure Message Attribute . . . . . . . . . . 13 93 2.4. Message Texts . . . . . . . . . . . . . . . . . . . . . . 13 94 3. State and Flow Diagram . . . . . . . . . . . . . . . . . . . 13 95 3.1. Not Authenticated State . . . . . . . . . . . . . . . . . 13 96 3.2. Authenticated State . . . . . . . . . . . . . . . . . . . 13 97 3.3. Selected State . . . . . . . . . . . . . . . . . . . . . 14 98 3.4. Logout State . . . . . . . . . . . . . . . . . . . . . . 14 99 4. Data Formats . . . . . . . . . . . . . . . . . . . . . . . . 16 100 4.1. Atom . . . . . . . . . . . . . . . . . . . . . . . . . . 16 101 4.1.1. Sequence set and UID set . . . . . . . . . . . . . . 16 102 4.2. Number . . . . . . . . . . . . . . . . . . . . . . . . . 16 103 4.3. String . . . . . . . . . . . . . . . . . . . . . . . . . 16 104 4.3.1. 8-bit and Binary Strings . . . . . . . . . . . . . . 17 105 4.4. Parenthesized List . . . . . . . . . . . . . . . . . . . 18 106 4.5. NIL . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 107 5. Operational Considerations . . . . . . . . . . . . . . . . . 19 108 5.1. Mailbox Naming . . . . . . . . . . . . . . . . . . . . . 19 109 5.1.1. Mailbox Hierarchy Naming . . . . . . . . . . . . . . 20 110 5.1.2. Namespaces . . . . . . . . . . . . . . . . . . . . . 20 111 5.2. Mailbox Size and Message Status Updates . . . . . . . . . 21 112 5.3. Response when no Command in Progress . . . . . . . . . . 22 113 5.4. Autologout Timer . . . . . . . . . . . . . . . . . . . . 22 114 5.5. Multiple Commands in Progress (Command Pipelining) . . . 22 115 6. Client Commands . . . . . . . . . . . . . . . . . . . . . . . 23 116 6.1. Client Commands - Any State . . . . . . . . . . . . . . . 24 117 6.1.1. CAPABILITY Command . . . . . . . . . . . . . . . . . 24 118 6.1.2. NOOP Command . . . . . . . . . . . . . . . . . . . . 25 119 6.1.3. LOGOUT Command . . . . . . . . . . . . . . . . . . . 26 120 6.2. Client Commands - Not Authenticated State . . . . . . . . 26 121 6.2.1. STARTTLS Command . . . . . . . . . . . . . . . . . . 27 122 6.2.2. AUTHENTICATE Command . . . . . . . . . . . . . . . . 28 123 6.2.3. LOGIN Command . . . . . . . . . . . . . . . . . . . . 31 124 6.3. Client Commands - Authenticated State . . . . . . . . . . 31 125 6.3.1. ENABLE Command . . . . . . . . . . . . . . . . . . . 32 126 6.3.2. SELECT Command . . . . . . . . . . . . . . . . . . . 34 127 6.3.3. EXAMINE Command . . . . . . . . . . . . . . . . . . . 35 128 6.3.4. CREATE Command . . . . . . . . . . . . . . . . . . . 36 129 6.3.5. DELETE Command . . . . . . . . . . . . . . . . . . . 37 130 6.3.6. RENAME Command . . . . . . . . . . . . . . . . . . . 38 131 6.3.7. SUBSCRIBE Command . . . . . . . . . . . . . . . . . . 40 132 6.3.8. UNSUBSCRIBE Command . . . . . . . . . . . . . . . . . 41 133 6.3.9. LIST Command . . . . . . . . . . . . . . . . . . . . 41 134 6.3.10. LSUB Command . . . . . . . . . . . . . . . . . . . . 58 135 6.3.11. NAMESPACE Command . . . . . . . . . . . . . . . . . . 59 136 6.3.12. STATUS Command . . . . . . . . . . . . . . . . . . . 63 137 6.3.13. APPEND Command . . . . . . . . . . . . . . . . . . . 65 138 6.3.14. IDLE Command . . . . . . . . . . . . . . . . . . . . 67 139 6.4. Client Commands - Selected State . . . . . . . . . . . . 69 140 6.4.1. CLOSE Command . . . . . . . . . . . . . . . . . . . . 69 141 6.4.2. UNSELECT Command . . . . . . . . . . . . . . . . . . 70 142 6.4.3. EXPUNGE Command . . . . . . . . . . . . . . . . . . . 70 143 6.4.4. SEARCH Command . . . . . . . . . . . . . . . . . . . 71 144 6.4.5. FETCH Command . . . . . . . . . . . . . . . . . . . . 77 145 6.4.6. STORE Command . . . . . . . . . . . . . . . . . . . . 81 146 6.4.7. COPY Command . . . . . . . . . . . . . . . . . . . . 82 147 6.4.8. MOVE Command . . . . . . . . . . . . . . . . . . . . 83 148 6.4.9. UID Command . . . . . . . . . . . . . . . . . . . . . 85 149 6.5. Client Commands - Experimental/Expansion . . . . . . . . 87 150 6.5.1. X Command . . . . . . . . . . . . . . . . . . . 87 151 7. Server Responses . . . . . . . . . . . . . . . . . . . . . . 87 152 7.1. Server Responses - Status Responses . . . . . . . . . . . 88 153 7.1.1. OK Response . . . . . . . . . . . . . . . . . . . . . 96 154 7.1.2. NO Response . . . . . . . . . . . . . . . . . . . . . 96 155 7.1.3. BAD Response . . . . . . . . . . . . . . . . . . . . 97 156 7.1.4. PREAUTH Response . . . . . . . . . . . . . . . . . . 97 157 7.1.5. BYE Response . . . . . . . . . . . . . . . . . . . . 97 158 7.2. Server Responses - Server and Mailbox Status . . . . . . 98 159 7.2.1. The ENABLED Response . . . . . . . . . . . . . . . . 98 160 7.2.2. CAPABILITY Response . . . . . . . . . . . . . . . . . 98 161 7.2.3. LIST Response . . . . . . . . . . . . . . . . . . . . 99 162 7.2.4. LSUB Response . . . . . . . . . . . . . . . . . . . . 102 163 7.2.5. NAMESPACE Response . . . . . . . . . . . . . . . . . 102 164 7.2.6. STATUS Response . . . . . . . . . . . . . . . . . . . 103 165 7.2.7. ESEARCH Response . . . . . . . . . . . . . . . . . . 103 166 7.2.8. FLAGS Response . . . . . . . . . . . . . . . . . . . 104 167 7.3. Server Responses - Mailbox Size . . . . . . . . . . . . . 104 168 7.3.1. EXISTS Response . . . . . . . . . . . . . . . . . . . 104 169 7.4. Server Responses - Message Status . . . . . . . . . . . . 104 170 7.4.1. EXPUNGE Response . . . . . . . . . . . . . . . . . . 104 171 7.4.2. FETCH Response . . . . . . . . . . . . . . . . . . . 105 172 7.5. Server Responses - Command Continuation Request . . . . . 111 173 8. Sample IMAP4rev2 connection . . . . . . . . . . . . . . . . . 112 174 9. Formal Syntax . . . . . . . . . . . . . . . . . . . . . . . . 113 175 10. Author's Note . . . . . . . . . . . . . . . . . . . . . . . . 128 176 11. Security Considerations . . . . . . . . . . . . . . . . . . . 128 177 11.1. STARTTLS Security Considerations . . . . . . . . . . . . 128 178 11.2. COPYUID and APPENDUID response codes . . . . . . . . . . 129 179 11.3. LIST command and Other Users' namespace . . . . . . . . 129 180 11.4. Other Security Considerations . . . . . . . . . . . . . 129 181 12. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 130 182 12.1. Updates to IMAP4 Capabilities registry . . . . . . . . . 130 183 12.2. GSSAPI/SASL service name . . . . . . . . . . . . . . . . 131 184 13. References . . . . . . . . . . . . . . . . . . . . . . . . . 131 185 13.1. Normative References . . . . . . . . . . . . . . . . . . 131 186 13.2. Informative References (related protocols) . . . . . . . 134 187 13.3. Informative References (historical aspects of IMAP and 188 related protocols) . . . . . . . . . . . . . . . . . . . 135 189 Appendix A. Backward compatibility with IMAP4rev1 . . . . . . . 136 190 A.1. Mailbox International Naming Convention . . . . . . . . . 136 191 Appendix B. Backward compatibility with BINARY extension . . . . 138 192 Appendix C. Changes from RFC 3501 / IMAP4rev1 . . . . . . . . . 138 193 Appendix D. Acknowledgement . . . . . . . . . . . . . . . . . . 140 194 Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 140 195 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 145 197 1. How to Read This Document 199 1.1. Organization of This Document 201 This document is written from the point of view of the implementor of 202 an IMAP4rev2 client or server. Beyond the protocol overview in 203 section 2, it is not optimized for someone trying to understand the 204 operation of the protocol. The material in sections 3 through 5 205 provides the general context and definitions with which IMAP4rev2 206 operates. 208 Sections 6, 7, and 9 describe the IMAP commands, responses, and 209 syntax, respectively. The relationships among these are such that it 210 is almost impossible to understand any of them separately. In 211 particular, do not attempt to deduce command syntax from the command 212 section alone; instead refer to the Formal Syntax section. 214 1.2. Conventions Used in This Document 216 "Conventions" are basic principles or procedures. Document 217 conventions are noted in this section. 219 In examples, "C:" and "S:" indicate lines sent by the client and 220 server respectively. 222 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 223 "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and 224 "OPTIONAL" in this document are to be interpreted as described in BCP 225 14 [RFC2119] [RFC8174] when, and only when, they appear in all 226 capitals, as shown here. 228 The word "can" (not "may") is used to refer to a possible 229 circumstance or situation, as opposed to an optional facility of the 230 protocol. 232 "User" is used to refer to a human user, whereas "client" refers to 233 the software being run by the user. 235 "Connection" refers to the entire sequence of client/server 236 interaction from the initial establishment of the network connection 237 until its termination. 239 "Session" refers to the sequence of client/server interaction from 240 the time that a mailbox is selected (SELECT or EXAMINE command) until 241 the time that selection ends (SELECT or EXAMINE of another mailbox, 242 CLOSE command, UNSELECT command, or connection termination). 244 Characters are 7-bit US-ASCII unless otherwise specified. Other 245 character sets are indicated using a "CHARSET", as described in 246 [MIME-IMT] and defined in [CHARSET]. CHARSETs have important 247 additional semantics in addition to defining character set; refer to 248 these documents for more detail. 250 There are several protocol conventions in IMAP. These refer to 251 aspects of the specification which are not strictly part of the IMAP 252 protocol, but reflect generally-accepted practice. Implementations 253 need to be aware of these conventions, and avoid conflicts whether or 254 not they implement the convention. For example, "&" may not be used 255 as a hierarchy delimiter since it conflicts with the Mailbox 256 International Naming Convention, and other uses of "&" in mailbox 257 names are impacted as well. 259 1.3. Special Notes to Implementors 261 Implementors of the IMAP protocol are strongly encouraged to read the 262 IMAP implementation recommendations document [IMAP-IMPLEMENTATION] in 263 conjunction with this document, to help understand the intricacies of 264 this protocol and how best to build an interoperable product. 266 IMAP4rev2 is designed to be upwards compatible from the [IMAP2] and 267 unpublished IMAP2bis protocols. IMAP4rev2 is largely compatible with 268 the IMAP4rev1 protocol described in RFC 3501 and the IMAP4 protocol 269 described in RFC 1730; the exception being in certain facilities 270 added in RFC 1730 that proved problematic and were subsequently 271 removed. In the course of the evolution of IMAP4rev2, some aspects 272 in the earlier protocols have become obsolete. Obsolete commands, 273 responses, and data formats which an IMAP4rev2 implementation can 274 encounter when used with an earlier implementation are described in 275 [IMAP-OBSOLETE]. 277 Other compatibility issues with IMAP2bis, the most common variant of 278 the earlier protocol, are discussed in [IMAP-COMPAT]. A full 279 discussion of compatibility issues with rare (and presumed extinct) 280 variants of [IMAP2] is in [IMAP-HISTORICAL]; this document is 281 primarily of historical interest. 283 IMAP was originally developed for the older [RFC-822] standard, and 284 as a consequence several fetch items in IMAP incorporate "RFC822" in 285 their name. With the exception of RFC822.SIZE, there are more modern 286 replacements; for example, the modern version of RFC822.HEADER is 287 BODY.PEEK[HEADER]. In all cases, "RFC822" should be interpreted as a 288 reference to the updated [RFC-5322] standard. 290 2. Protocol Overview 292 2.1. Link Level 294 The IMAP4rev2 protocol assumes a reliable data stream such as that 295 provided by TCP. When TCP is used, an IMAP4rev2 server listens on 296 port 143. 298 2.2. Commands and Responses 300 An IMAP4rev2 connection consists of the establishment of a client/ 301 server network connection, an initial greeting from the server, and 302 client/server interactions. These client/server interactions consist 303 of a client command, server data, and a server completion result 304 response. 306 All interactions transmitted by client and server are in the form of 307 lines, that is, strings that end with a CRLF. The protocol receiver 308 of an IMAP4rev2 client or server is either reading a line, or is 309 reading a sequence of octets with a known count followed by a line. 311 2.2.1. Client Protocol Sender and Server Protocol Receiver 313 The client command begins an operation. Each client command is 314 prefixed with an identifier (typically a short alphanumeric string, 315 e.g., A0001, A0002, etc.) called a "tag". A different tag is 316 generated by the client for each command. 318 Clients MUST follow the syntax outlined in this specification 319 strictly. It is a syntax error to send a command with missing or 320 extraneous spaces or arguments. 322 There are two cases in which a line from the client does not 323 represent a complete command. In one case, a command argument is 324 quoted with an octet count (see the description of literal in String 325 under Data Formats); in the other case, the command arguments require 326 server feedback (see the AUTHENTICATE command). In either case, the 327 server sends a command continuation request response if it is ready 328 for the octets (if appropriate) and the remainder of the command. 329 This response is prefixed with the token "+". 331 Note: If instead, the server detected an error in the command, it 332 sends a BAD completion response with a tag matching the command 333 (as described below) to reject the command and prevent the client 334 from sending any more of the command. 336 It is also possible for the server to send a completion response 337 for some other command (if multiple commands are in progress), or 338 untagged data. In either case, the command continuation request 339 is still pending; the client takes the appropriate action for the 340 response, and reads another response from the server. In all 341 cases, the client MUST send a complete command (including 342 receiving all command continuation request responses and command 343 continuations for the command) before initiating a new command. 345 The protocol receiver of an IMAP4rev2 server reads a command line 346 from the client, parses the command and its arguments, and transmits 347 server data and a server command completion result response. 349 2.2.2. Server Protocol Sender and Client Protocol Receiver 351 Data transmitted by the server to the client and status responses 352 that do not indicate command completion are prefixed with the token 353 "*", and are called untagged responses. 355 Server data MAY be sent as a result of a client command, or MAY be 356 sent unilaterally by the server. There is no syntactic difference 357 between server data that resulted from a specific command and server 358 data that were sent unilaterally. 360 The server completion result response indicates the success or 361 failure of the operation. It is tagged with the same tag as the 362 client command which began the operation. Thus, if more than one 363 command is in progress, the tag in a server completion response 364 identifies the command to which the response applies. There are 365 three possible server completion responses: OK (indicating success), 366 NO (indicating failure), or BAD (indicating a protocol error such as 367 unrecognized command or command syntax error). 369 Servers SHOULD enforce the syntax outlined in this specification 370 strictly. Any client command with a protocol syntax error, including 371 (but not limited to) missing or extraneous spaces or arguments, 372 SHOULD be rejected, and the client given a BAD server completion 373 response. 375 The protocol receiver of an IMAP4rev2 client reads a response line 376 from the server. It then takes action on the response based upon the 377 first token of the response, which can be a tag, a "*", or a "+". 379 A client MUST be prepared to accept any server response at all times. 380 This includes server data that was not requested. Server data SHOULD 381 be recorded, so that the client can reference its recorded copy 382 rather than sending a command to the server to request the data. In 383 the case of certain server data, the data MUST be recorded. 385 This topic is discussed in greater detail in the Server Responses 386 section. 388 2.3. Message Attributes 390 In addition to message text, each message has several attributes 391 associated with it. These attributes can be retrieved individually 392 or in conjunction with other attributes or message texts. 394 2.3.1. Message Numbers 396 Messages in IMAP4rev2 are accessed by one of two numbers; the unique 397 identifier or the message sequence number. 399 2.3.1.1. Unique Identifier (UID) Message Attribute 401 An unsigned 32-bit value assigned to each message, which when used 402 with the unique identifier validity value (see below) forms a 64-bit 403 value that MUST NOT refer to any other message in the mailbox or any 404 subsequent mailbox with the same name forever. Unique identifiers 405 are assigned in a strictly ascending fashion in the mailbox; as each 406 message is added to the mailbox it is assigned a higher UID than the 407 message(s) which were added previously. Unlike message sequence 408 numbers, unique identifiers are not necessarily contiguous. 410 The unique identifier of a message MUST NOT change during the 411 session, and SHOULD NOT change between sessions. Any change of 412 unique identifiers between sessions MUST be detectable using the 413 UIDVALIDITY mechanism discussed below. Persistent unique identifiers 414 are required for a client to resynchronize its state from a previous 415 session with the server (e.g., disconnected or offline access 416 clients); this is discussed further in [IMAP-DISC]. 418 Associated with every mailbox are two 32-bit unsigned values which 419 aid in unique identifier handling: the next unique identifier value 420 (UIDNEXT) and the unique identifier validity value (UIDVALIDITY). 422 The next unique identifier value is the predicted value that will be 423 assigned to a new message in the mailbox. Unless the unique 424 identifier validity also changes (see below), the next unique 425 identifier value MUST have the following two characteristics. First, 426 the next unique identifier value MUST NOT change unless new messages 427 are added to the mailbox; and second, the next unique identifier 428 value MUST change whenever new messages are added to the mailbox, 429 even if those new messages are subsequently expunged. 431 Note: The next unique identifier value is intended to provide a 432 means for a client to determine whether any messages have been 433 delivered to the mailbox since the previous time it checked this 434 value. It is not intended to provide any guarantee that any 435 message will have this unique identifier. A client can only 436 assume, at the time that it obtains the next unique identifier 437 value, that messages arriving after that time will have a UID 438 greater than or equal to that value. 440 The unique identifier validity value is sent in a UIDVALIDITY 441 response code in an OK untagged response at mailbox selection time. 442 If unique identifiers from an earlier session fail to persist in this 443 session, the unique identifier validity value MUST be greater than 444 the one used in the earlier session. 446 Note: Ideally, unique identifiers SHOULD persist at all times. 447 Although this specification recognizes that failure to persist can 448 be unavoidable in certain server environments, it STRONGLY 449 ENCOURAGES message store implementation techniques that avoid this 450 problem. For example: 452 1. Unique identifiers MUST be strictly ascending in the mailbox 453 at all times. If the physical message store is re-ordered by 454 a non-IMAP agent, this requires that the unique identifiers in 455 the mailbox be regenerated, since the former unique 456 identifiers are no longer strictly ascending as a result of 457 the re-ordering. 459 2. If the message store has no mechanism to store unique 460 identifiers, it must regenerate unique identifiers at each 461 session, and each session must have a unique UIDVALIDITY 462 value. 464 3. If the mailbox is deleted and a new mailbox with the same name 465 is created at a later date, the server must either keep track 466 of unique identifiers from the previous instance of the 467 mailbox, or it must assign a new UIDVALIDITY value to the new 468 instance of the mailbox. A good UIDVALIDITY value to use in 469 this case is a 32-bit representation of the creation date/time 470 of the mailbox. It is alright to use a constant such as 1, 471 but only if it guaranteed that unique identifiers will never 472 be reused, even in the case of a mailbox being deleted (or 473 renamed) and a new mailbox by the same name created at some 474 future time. 476 4. The combination of mailbox name, UIDVALIDITY, and UID must 477 refer to a single immutable message on that server forever. 478 In particular, the internal date, [RFC-5322] size, envelope, 479 body structure, and message texts (RFC822, RFC822.HEADER, 480 RFC822.TEXT, and all BODY[...] fetch data items) must never 481 change. This does not include message numbers, nor does it 482 include attributes that can be set by a STORE command (e.g., 483 FLAGS). 485 2.3.1.2. Message Sequence Number Message Attribute 487 A relative position from 1 to the number of messages in the mailbox. 488 This position MUST be ordered by ascending unique identifier. As 489 each new message is added, it is assigned a message sequence number 490 that is 1 higher than the number of messages in the mailbox before 491 that new message was added. 493 Message sequence numbers can be reassigned during the session. For 494 example, when a message is permanently removed (expunged) from the 495 mailbox, the message sequence number for all subsequent messages is 496 decremented. The number of messages in the mailbox is also 497 decremented. Similarly, a new message can be assigned a message 498 sequence number that was once held by some other message prior to an 499 expunge. 501 In addition to accessing messages by relative position in the 502 mailbox, message sequence numbers can be used in mathematical 503 calculations. For example, if an untagged "11 EXISTS" is received, 504 and previously an untagged "8 EXISTS" was received, three new 505 messages have arrived with message sequence numbers of 9, 10, and 11. 506 Another example, if message 287 in a 523 message mailbox has UID 507 12345, there are exactly 286 messages which have lesser UIDs and 236 508 messages which have greater UIDs. 510 2.3.2. Flags Message Attribute 512 A list of zero or more named tokens associated with the message. A 513 flag is set by its addition to this list, and is cleared by its 514 removal. There are two types of flags in IMAP4rev2. A flag of 515 either type can be permanent or session-only. 517 A system flag is a flag name that is pre-defined in this 518 specification and begin with "\". Certain system flags (\Deleted and 519 \Seen) have special semantics described elsewhere in this document. 520 The currently-defined system flags are: 522 \Seen Message has been read 524 \Answered Message has been answered 526 \Flagged Message is "flagged" for urgent/special attention 528 \Deleted Message is "deleted" for removal by later EXPUNGE 529 \Draft Message has not completed composition (marked as a draft). 531 \Recent This flag was in used in IMAP4rev1 and is now deprecated. 533 A keyword is defined by the server implementation. Keywords do not 534 begin with "\". Servers MAY permit the client to define new keywords 535 in the mailbox (see the description of the PERMANENTFLAGS response 536 code for more information). Some keywords that start with "$" are 537 also defined in this specification. 539 This document defines several keywords that were not originally 540 defined in RFC 3501, but which were found to be useful by client 541 implementations. These keywords SHOULD be supported (i.e. allowed in 542 APPEND, COPY, MOVE and SEARCH commands) by server implementations: 544 $Forwarded Message has been forwarded to another email address, 545 embedded within or attached to a new message. An email client 546 sets this keyword when it successfully forwards the message to 547 another email address. Typical usage of this keyword is to show a 548 different (or additional) icon for a message that has been 549 forwarded. Once set, the flag SHOULD NOT be cleared. 551 $MDNSent Message Disposition Notification [RFC8098] was generated 552 and sent for this message. 554 A flag can be permanent or session-only on a per-flag basis. 555 Permanent flags are those which the client can add or remove from the 556 message flags permanently; that is, concurrent and subsequent 557 sessions will see any change in permanent flags. Changes to session 558 flags are valid only in that session. 560 2.3.3. Internal Date Message Attribute 562 The internal date and time of the message on the server. This is not 563 the date and time in the [RFC-5322] header, but rather a date and 564 time which reflects when the message was received. In the case of 565 messages delivered via [SMTP], this SHOULD be the date and time of 566 final delivery of the message as defined by [SMTP]. In the case of 567 messages delivered by the IMAP4rev2 COPY or MOVE command, this SHOULD 568 be the internal date and time of the source message. In the case of 569 messages delivered by the IMAP4rev2 APPEND command, this SHOULD be 570 the date and time as specified in the APPEND command description. 571 All other cases are implementation defined. 573 2.3.4. [RFC-5322] Size Message Attribute 575 The number of octets in the message, as expressed in [RFC-5322] 576 format. 578 2.3.5. Envelope Structure Message Attribute 580 A parsed representation of the [RFC-5322] header of the message. 581 Note that the IMAP Envelope structure is not the same as an [SMTP] 582 envelope. 584 2.3.6. Body Structure Message Attribute 586 A parsed representation of the [MIME-IMB] body structure information 587 of the message. 589 2.4. Message Texts 591 In addition to being able to fetch the full [RFC-5322] text of a 592 message, IMAP4rev2 permits the fetching of portions of the full 593 message text. Specifically, it is possible to fetch the [RFC-5322] 594 message header, [RFC-5322] message body, a [MIME-IMB] body part, or a 595 [MIME-IMB] header. 597 3. State and Flow Diagram 599 Once the connection between client and server is established, an 600 IMAP4rev2 connection is in one of four states. The initial state is 601 identified in the server greeting. Most commands are only valid in 602 certain states. It is a protocol error for the client to attempt a 603 command while the connection is in an inappropriate state, and the 604 server will respond with a BAD or NO (depending upon server 605 implementation) command completion result. 607 3.1. Not Authenticated State 609 In the not authenticated state, the client MUST supply authentication 610 credentials before most commands will be permitted. This state is 611 entered when a connection starts unless the connection has been pre- 612 authenticated. 614 3.2. Authenticated State 616 In the authenticated state, the client is authenticated and MUST 617 select a mailbox to access before commands that affect messages will 618 be permitted. This state is entered when a pre-authenticated 619 connection starts, when acceptable authentication credentials have 620 been provided, after an error in selecting a mailbox, or after a 621 successful CLOSE command. 623 3.3. Selected State 625 In a selected state, a mailbox has been selected to access. This 626 state is entered when a mailbox has been successfully selected. 628 3.4. Logout State 630 In the logout state, the connection is being terminated. This state 631 can be entered as a result of a client request (via the LOGOUT 632 command) or by unilateral action on the part of either the client or 633 server. 635 If the client requests the logout state, the server MUST send an 636 untagged BYE response and a tagged OK response to the LOGOUT command 637 before the server closes the connection; and the client MUST read the 638 tagged OK response to the LOGOUT command before the client closes the 639 connection. 641 A server SHOULD NOT unilaterally close the connection without sending 642 an untagged BYE response that contains the reason for having done so. 643 A client SHOULD NOT unilaterally close the connection, and instead 644 SHOULD issue a LOGOUT command. If the server detects that the client 645 has unilaterally closed the connection, the server MAY omit the 646 untagged BYE response and simply close its connection. 648 +----------------------+ 649 |connection established| 650 +----------------------+ 651 || 652 \/ 653 +--------------------------------------+ 654 | server greeting | 655 +--------------------------------------+ 656 || (1) || (2) || (3) 657 \/ || || 658 +-----------------+ || || 659 |Not Authenticated| || || 660 +-----------------+ || || 661 || (7) || (4) || || 662 || \/ \/ || 663 || +----------------+ || 664 || | Authenticated |<=++ || 665 || +----------------+ || || 666 || || (7) || (5) || (6) || 667 || || \/ || || 668 || || +--------+ || || 669 || || |Selected|==++ || 670 || || +--------+ || 671 || || || (7) || 672 \/ \/ \/ \/ 673 +--------------------------------------+ 674 | Logout | 675 +--------------------------------------+ 676 || 677 \/ 678 +-------------------------------+ 679 |both sides close the connection| 680 +-------------------------------+ 682 (1) connection without pre-authentication (OK greeting) 683 (2) pre-authenticated connection (PREAUTH greeting) 684 (3) rejected connection (BYE greeting) 685 (4) successful LOGIN or AUTHENTICATE command 686 (5) successful SELECT or EXAMINE command 687 (6) CLOSE command, unsolicited CLOSED response code or 688 failed SELECT or EXAMINE command 689 (7) LOGOUT command, server shutdown, or connection closed 691 4. Data Formats 693 IMAP4rev2 uses textual commands and responses. Data in IMAP4rev2 can 694 be in one of several forms: atom, number, string, parenthesized list, 695 or NIL. Note that a particular data item may take more than one 696 form; for example, a data item defined as using "astring" syntax may 697 be either an atom or a string. 699 4.1. Atom 701 An atom consists of one or more non-special characters. 703 4.1.1. Sequence set and UID set 705 A set of messages can be referenced by a sequence set containing 706 either message sequence numbers or unique identifiers. See Section 9 707 for details. Sequence sets can contain ranges (e.g. "5:50"), an 708 enumeration of specific message/UID numbers, a special symbol "*", or 709 a combination of the above. 711 A "UID set" is similar to the sequence set of unique identifiers; 712 however, the "*" value for a sequence number is not permitted. 714 4.2. Number 716 A number consists of one or more digit characters, and represents a 717 numeric value. 719 4.3. String 721 A string is in one of three forms: synchonizing literal, non- 722 synchronizing literal or quoted string. The synchronizing literal 723 form is the general form of string. The non-synchronizing literal 724 form is also the general form, but has length limitation. The quoted 725 string form is an alternative that avoids the overhead of processing 726 a literal at the cost of limitations of characters which may be used. 728 When the distinction between synchronizing and non-synchronizing 729 literals is not important, this document just uses the term 730 "literal". 732 A synchronizing literal is a sequence of zero or more octets 733 (including CR and LF), prefix-quoted with an octet count in the form 734 of an open brace ("{"), the number of octets, close brace ("}"), and 735 CRLF. In the case of synchronizing literals transmitted from server 736 to client, the CRLF is immediately followed by the octet data. In 737 the case of synchronizing literals transmitted from client to server, 738 the client MUST wait to receive a command continuation request 739 (described later in this document) before sending the octet data (and 740 the remainder of the command). 742 The non-synchronizing literal is an alternate form of synchronizing 743 literal, and it may appear in communication from client to server 744 instead of the synchonizing form of literal. The non-synchronizing 745 literal form MUST NOT be sent from server to client. The non- 746 synchronizing literal is distinguished from the synchronizing literal 747 by having a plus ("+") between the octet count and the closing brace 748 ("}"). The server does not generate a command continuation request 749 in response to a non-synchronizing literal, and clients are not 750 required to wait before sending the octets of a non- synchronizing 751 literal. Non-synchronizing literals MUST NOT be larger than 4096 752 octets. Any literal larger than 4096 bytes MUST be sent as a 753 synchronizing literal. (Non-synchronizing literals defined in this 754 document are the same as non-synchronizing literals defined by the 755 LITERAL- extension from [RFC7888]. See that document for details on 756 how to handle invalid non-synchronizing literals longer than 4096 757 octets and for interaction with other IMAP extensions.) 759 A quoted string is a sequence of zero or more Unicode characters, 760 excluding CR and LF, encoded in UTF-8, with double quote (<">) 761 characters at each end. 763 The empty string is represented as "" (a quoted string with zero 764 characters between double quotes), as {0} followed by CRLF (a 765 synchronizing literal with an octet count of 0) or as {0+} followed 766 by CRLF (a non-synchronizing literal with an octet count of 0). 768 Note: Even if the octet count is 0, a client transmitting a 769 synchronizing literal MUST wait to receive a command continuation 770 request. 772 4.3.1. 8-bit and Binary Strings 774 8-bit textual and binary mail is supported through the use of a 775 [MIME-IMB] content transfer encoding. IMAP4rev2 implementations MAY 776 transmit 8-bit or multi-octet characters in literals, but SHOULD do 777 so only when the [CHARSET] is identified. 779 IMAP4rev2 is compatible with [I18N-HDRS]. As a result, the 780 identified charset for header-field values with 8-bit content is 781 UTF-8 [UTF-8]. IMAP4rev2 implementations MUST accept and MAY 782 transmit [UTF-8] text in quoted-strings as long as the string does 783 not contain NUL, CR, or LF. This differs from IMAP4rev1 784 implementations. 786 Although a BINARY content transfer encoding is defined, unencoded 787 binary strings are not permitted, unless returned in a in 788 response to BINARY.PEEK[]<> or 789 BINARY[]<> FETCH data item. A "binary 790 string" is any string with NUL characters. A string with an 791 excessive amount of CTL characters MAY also be considered to be 792 binary. Unless returned in response to BINARY.PEEK[...]/BINARY[...] 793 FETCH, client and server implementations MUST encode binary data into 794 a textual form, such as BASE64, before transmitting the data. 796 4.4. Parenthesized List 798 Data structures are represented as a "parenthesized list"; a sequence 799 of data items, delimited by space, and bounded at each end by 800 parentheses. A parenthesized list can contain other parenthesized 801 lists, using multiple levels of parentheses to indicate nesting. 803 The empty list is represented as () -- a parenthesized list with no 804 members. 806 4.5. NIL 808 The special form "NIL" represents the non-existence of a particular 809 data item that is represented as a string or parenthesized list, as 810 distinct from the empty string "" or the empty parenthesized list (). 812 Note: NIL is never used for any data item which takes the form of 813 an atom. For example, a mailbox name of "NIL" is a mailbox named 814 NIL as opposed to a non-existent mailbox name. This is because 815 mailbox uses "astring" syntax which is an atom or a string. 816 Conversely, an addr-name of NIL is a non-existent personal name, 817 because addr-name uses "nstring" syntax which is NIL or a string, 818 but never an atom. 820 Examples: 822 The following LIST response: 824 * LIST () "/" NIL 826 is equivalent to: 827 * LIST () "/" "NIL" 829 as LIST response ABNF is using astring for mailbox name. 831 However, the following response 833 * FETCH 1 (BODY[1] NIL) 835 is not equivalent to: 836 * FETCH 1 (BODY[1] "NIL") 837 The former means absence of the body part, while the latter 838 means that it contains literal sequence of characters "NIL". 840 5. Operational Considerations 842 The following rules are listed here to ensure that all IMAP4rev2 843 implementations interoperate properly. 845 5.1. Mailbox Naming 847 In IMAP4rev2, Mailbox names are encoded in Net-Unicode [NET-UNICODE] 848 (this differs from IMAP4rev1). Client implementations MAY attempt to 849 create Net-Unicode mailbox names, and MUST interpret any 8-bit 850 mailbox names returned by LIST or LSUB as [NET-UNICODE]. Server 851 implementations MUST prohibit the creation of 8-bit mailbox names 852 that do not comply with Net-Unicode (however, servers MAY accept a 853 de-normalized UTF-8 mailbox name and convert it to Net-Unicode prior 854 to mailbox creation). 856 The case-insensitive mailbox name INBOX is a special name reserved to 857 mean "the primary mailbox for this user on this server". (Note that 858 this special name may not exist on some servers for some users.) The 859 interpretation of all other names is implementation-dependent. 861 In particular, this specification takes no position on case 862 sensitivity in non-INBOX mailbox names. Some server implementations 863 are fully case-sensitive in ASCII range; others preserve case of a 864 newly-created name but otherwise are case-insensitive; and yet others 865 coerce names to a particular case. Client implementations MUST 866 interact with any of these. 868 There are certain client considerations when creating a new mailbox 869 name: 871 1. Any character which is one of the atom-specials (see the Formal 872 Syntax) will require that the mailbox name be represented as a 873 quoted string or literal. 875 2. CTL and other non-graphic characters are difficult to represent 876 in a user interface and are best avoided. Servers MAY refuse to 877 create mailbox names containing Unicode CTL characters. 879 3. Although the list-wildcard characters ("%" and "*") are valid in 880 a mailbox name, it is difficult to use such mailbox names with 881 the LIST and LSUB commands due to the conflict with wildcard 882 interpretation. 884 4. Usually, a character (determined by the server implementation) is 885 reserved to delimit levels of hierarchy. 887 5. Two characters, "#" and "&", have meanings by convention, and 888 should be avoided except when used in that convention. 890 5.1.1. Mailbox Hierarchy Naming 892 If it is desired to export hierarchical mailbox names, mailbox names 893 MUST be left-to-right hierarchical using a single character to 894 separate levels of hierarchy. The same hierarchy separator character 895 is used for all levels of hierarchy within a single name. 897 5.1.2. Namespaces 899 Personal Namespace: A namespace that the server considers within the 900 personal scope of the authenticated user on a particular connection. 901 Typically, only the authenticated user has access to mailboxes in 902 their Personal Namespace. It is the part of the namespace that 903 belongs to the user that is allocated for mailboxes. If an INBOX 904 exists for a user, it MUST appear within the user's personal 905 namespace. In the typical case, there SHOULD be only one Personal 906 Namespace on a server. 908 Other Users' Namespace: A namespace that consists of mailboxes from 909 the Personal Namespaces of other users. To access mailboxes in the 910 Other Users' Namespace, the currently authenticated user MUST be 911 explicitly granted access rights. For example, it is common for a 912 manager to grant to their secretary access rights to their mailbox. 913 In the typical case, there SHOULD be only one Other Users' Namespace 914 on a server. 916 Shared Namespace: A namespace that consists of mailboxes that are 917 intended to be shared amongst users and do not exist within a user's 918 Personal Namespace. 920 The namespaces a server uses MAY differ on a per-user basis. 922 5.1.2.1. Historic Mailbox Namespace Naming Convention 924 By convention, the first hierarchical element of any mailbox name 925 which begins with "#" identifies the "namespace" of the remainder of 926 the name. This makes it possible to disambiguate between different 927 types of mailbox stores, each of which have their own namespaces. 929 For example, implementations which offer access to USENET 930 newsgroups MAY use the "#news" namespace to partition the USENET 931 newsgroup namespace from that of other mailboxes. Thus, the 932 comp.mail.misc newsgroup would have a mailbox name of 933 "#news.comp.mail.misc", and the name "comp.mail.misc" can refer to 934 a different object (e.g., a user's private mailbox). 936 Namespaces that include the "#" character are not IMAP URL [IMAP-URL] 937 friendly requiring the "#" character to be represented as %23 when 938 within URLs. As such, server implementers MAY instead consider using 939 namespace prefixes that do not contain the "#" character. 941 5.1.2.2. Common namespace models 943 Previous version of this protocol does not define a default server 944 namespace. Two common namespace models have evolved: 946 The "Personal Mailbox" model, in which the default namespace that is 947 presented consists of only the user's personal mailboxes. To access 948 shared mailboxes, the user must use an escape mechanism to reach 949 another namespace. 951 The "Complete Hierarchy" model, in which the default namespace that 952 is presented includes the user's personal mailboxes along with any 953 other mailboxes they have access to. 955 5.2. Mailbox Size and Message Status Updates 957 At any time, a server can send data that the client did not request. 958 Sometimes, such behavior is REQUIRED. For example, agents other than 959 the server MAY add messages to the mailbox (e.g., new message 960 delivery), change the flags of the messages in the mailbox (e.g., 961 simultaneous access to the same mailbox by multiple agents), or even 962 remove messages from the mailbox. A server MUST send mailbox size 963 updates automatically if a mailbox size change is observed during the 964 processing of a command. A server SHOULD send message flag updates 965 automatically, without requiring the client to request such updates 966 explicitly. 968 Special rules exist for server notification of a client about the 969 removal of messages to prevent synchronization errors; see the 970 description of the EXPUNGE response for more detail. In particular, 971 it is NOT permitted to send an EXISTS response that would reduce the 972 number of messages in the mailbox; only the EXPUNGE response can do 973 this. 975 Regardless of what implementation decisions a client makes on 976 remembering data from the server, a client implementation MUST record 977 mailbox size updates. It MUST NOT assume that any command after the 978 initial mailbox selection will return the size of the mailbox. 980 5.3. Response when no Command in Progress 982 Server implementations are permitted to send an untagged response 983 (except for EXPUNGE) while there is no command in progress. Server 984 implementations that send such responses MUST deal with flow control 985 considerations. Specifically, they MUST either (1) verify that the 986 size of the data does not exceed the underlying transport's available 987 window size, or (2) use non-blocking writes. 989 5.4. Autologout Timer 991 If a server has an inactivity autologout timer that applies to 992 sessions after authentication, the duration of that timer MUST be at 993 least 30 minutes. The receipt of ANY command from the client during 994 that interval SHOULD suffice to reset the autologout timer. 996 5.5. Multiple Commands in Progress (Command Pipelining) 998 The client MAY send another command without waiting for the 999 completion result response of a command, subject to ambiguity rules 1000 (see below) and flow control constraints on the underlying data 1001 stream. Similarly, a server MAY begin processing another command 1002 before processing the current command to completion, subject to 1003 ambiguity rules. However, any command continuation request responses 1004 and command continuations MUST be negotiated before any subsequent 1005 command is initiated. 1007 The exception is if an ambiguity would result because of a command 1008 that would affect the results of other commands. Clients MUST NOT 1009 send multiple commands without waiting if an ambiguity would result. 1010 If the server detects a possible ambiguity, it MUST execute commands 1011 to completion in the order given by the client. 1013 The most obvious example of ambiguity is when a command would affect 1014 the results of another command, e.g., a FETCH of a message's flags 1015 and a STORE of that same message's flags. 1017 A non-obvious ambiguity occurs with commands that permit an untagged 1018 EXPUNGE response (commands other than FETCH, STORE, and SEARCH), 1019 since an untagged EXPUNGE response can invalidate sequence numbers in 1020 a subsequent command. This is not a problem for FETCH, STORE, or 1021 SEARCH commands because servers are prohibited from sending EXPUNGE 1022 responses while any of those commands are in progress. Therefore, if 1023 the client sends any command other than FETCH, STORE, or SEARCH, it 1024 MUST wait for the completion result response before sending a command 1025 with message sequence numbers. 1027 Note: EXPUNGE responses are permitted while UID FETCH, UID STORE, 1028 and UID SEARCH are in progress. If the client sends a UID 1029 command, it MUST wait for a completion result response before 1030 sending a command which uses message sequence numbers (this may 1031 include UID SEARCH). Any message sequence numbers in an argument 1032 to UID SEARCH are associated with messages prior to the effect of 1033 any untagged EXPUNGE returned by the UID SEARCH. 1035 For example, the following non-waiting command sequences are invalid: 1037 FETCH + NOOP + STORE 1039 STORE + COPY + FETCH 1041 COPY + COPY 1043 The following are examples of valid non-waiting command sequences: 1045 FETCH + STORE + SEARCH + NOOP 1047 STORE + COPY + EXPUNGE 1049 UID SEARCH + UID SEARCH may be valid or invalid as a non-waiting 1050 command sequence, depending upon whether or not the second UID 1051 SEARCH contains message sequence numbers. 1053 6. Client Commands 1055 IMAP4rev2 commands are described in this section. Commands are 1056 organized by the state in which the command is permitted. Commands 1057 which are permitted in multiple states are listed in the minimum 1058 permitted state (for example, commands valid in authenticated and 1059 selected state are listed in the authenticated state commands). 1061 Command arguments, identified by "Arguments:" in the command 1062 descriptions below, are described by function, not by syntax. The 1063 precise syntax of command arguments is described in the Formal Syntax 1064 (Section 9). 1066 Some commands cause specific server responses to be returned; these 1067 are identified by "Responses:" in the command descriptions below. 1068 See the response descriptions in the Responses section for 1069 information on these responses, and the Formal Syntax section for the 1070 precise syntax of these responses. It is possible for server data to 1071 be transmitted as a result of any command. Thus, commands that do 1072 not specifically require server data specify "no specific responses 1073 for this command" instead of "none". 1075 The "Result:" in the command description refers to the possible 1076 tagged status responses to a command, and any special interpretation 1077 of these status responses. 1079 The state of a connection is only changed by successful commands 1080 which are documented as changing state. A rejected command (BAD 1081 response) never changes the state of the connection or of the 1082 selected mailbox. A failed command (NO response) generally does not 1083 change the state of the connection or of the selected mailbox; the 1084 exception being the SELECT and EXAMINE commands. 1086 6.1. Client Commands - Any State 1088 The following commands are valid in any state: CAPABILITY, NOOP, and 1089 LOGOUT. 1091 6.1.1. CAPABILITY Command 1093 Arguments: none 1095 Responses: REQUIRED untagged response: CAPABILITY 1097 Result: OK - capability completed 1098 BAD - command unknown or arguments invalid 1100 The CAPABILITY command requests a listing of capabilities that the 1101 server supports. The server MUST send a single untagged CAPABILITY 1102 response with "IMAP4rev2" as one of the listed capabilities before 1103 the (tagged) OK response. 1105 A capability name which begins with "AUTH=" indicates that the server 1106 supports that particular authentication mechanism. All such names 1107 are, by definition, part of this specification. For example, the 1108 authorization capability for an experimental "blurdybloop" 1109 authenticator would be "AUTH=XBLURDYBLOOP" and not 1110 "XAUTH=BLURDYBLOOP" or "XAUTH=XBLURDYBLOOP". 1112 Other capability names refer to extensions, revisions, or amendments 1113 to this specification. See the documentation of the CAPABILITY 1114 response for additional information. No capabilities, beyond the 1115 base IMAP4rev2 set defined in this specification, are enabled without 1116 explicit client action to invoke the capability. 1118 Client and server implementations MUST implement the STARTTLS, 1119 LOGINDISABLED, and AUTH=PLAIN (described in [PLAIN]) capabilities. 1120 See the Security Considerations section for important information. 1122 See the section entitled "Client Commands - Experimental/Expansion" 1123 for information about the form of site or implementation-specific 1124 capabilities. 1126 Example: C: abcd CAPABILITY 1127 S: * CAPABILITY IMAP4rev2 STARTTLS AUTH=GSSAPI 1128 LOGINDISABLED 1129 S: abcd OK CAPABILITY completed 1130 C: efgh STARTTLS 1131 S: efgh OK STARTLS completed 1132 1133 C: ijkl CAPABILITY 1134 S: * CAPABILITY IMAP4rev2 AUTH=GSSAPI AUTH=PLAIN 1135 S: ijkl OK CAPABILITY completed 1137 6.1.2. NOOP Command 1139 Arguments: none 1141 Responses: no specific responses for this command (but see below) 1143 Result: OK - noop completed 1144 BAD - command unknown or arguments invalid 1146 The NOOP command always succeeds. It does nothing. 1148 Since any command can return a status update as untagged data, the 1149 NOOP command can be used as a periodic poll for new messages or 1150 message status updates during a period of inactivity (the IDLE 1151 command Section 6.3.14 should be used instead of NOOP if real-time 1152 updates to mailbox state are desirable). The NOOP command can also 1153 be used to reset any inactivity autologout timer on the server. 1155 Example: C: a002 NOOP 1156 S: a002 OK NOOP completed 1157 . . . 1158 C: a047 NOOP 1159 S: * 22 EXPUNGE 1160 S: * 23 EXISTS 1161 S: * 14 FETCH (UID 1305 FLAGS (\Seen \Deleted)) 1162 S: a047 OK NOOP completed 1164 6.1.3. LOGOUT Command 1166 Arguments: none 1168 Responses: REQUIRED untagged response: BYE 1170 Result: OK - logout completed 1171 BAD - command unknown or arguments invalid 1173 The LOGOUT command informs the server that the client is done with 1174 the connection. The server MUST send a BYE untagged response before 1175 the (tagged) OK response, and then close the network connection. 1177 Example: C: A023 LOGOUT 1178 S: * BYE IMAP4rev2 Server logging out 1179 S: A023 OK LOGOUT completed 1180 (Server and client then close the connection) 1182 6.2. Client Commands - Not Authenticated State 1184 In the not authenticated state, the AUTHENTICATE or LOGIN command 1185 establishes authentication and enters the authenticated state. The 1186 AUTHENTICATE command provides a general mechanism for a variety of 1187 authentication techniques, privacy protection, and integrity 1188 checking; whereas the LOGIN command uses a traditional user name and 1189 plaintext password pair and has no means of establishing privacy 1190 protection or integrity checking. 1192 The STARTTLS command is an alternate form of establishing session 1193 privacy protection and integrity checking, but does not by itself 1194 establish authentication or enter the authenticated state. 1196 Server implementations MAY allow access to certain mailboxes without 1197 establishing authentication. This can be done by means of the 1198 ANONYMOUS [SASL] authenticator described in [ANONYMOUS]. An older 1199 convention is a LOGIN command using the userid "anonymous"; in this 1200 case, a password is required although the server may choose to accept 1201 any password. The restrictions placed on anonymous users are 1202 implementation-dependent. 1204 Once authenticated (including as anonymous), it is not possible to 1205 re-enter not authenticated state. 1207 In addition to the universal commands (CAPABILITY, NOOP, and LOGOUT), 1208 the following commands are valid in the not authenticated state: 1209 STARTTLS, AUTHENTICATE and LOGIN. See the Security Considerations 1210 section for important information about these commands. 1212 6.2.1. STARTTLS Command 1214 Arguments: none 1216 Responses: no specific response for this command 1218 Result: OK - starttls completed, begin TLS negotiation 1219 BAD - command unknown or arguments invalid 1221 A [TLS] negotiation begins immediately after the CRLF at the end of 1222 the tagged OK response from the server. Once a client issues a 1223 STARTTLS command, it MUST NOT issue further commands until a server 1224 response is seen and the [TLS] negotiation is complete. 1226 The server remains in the non-authenticated state, even if client 1227 credentials are supplied during the [TLS] negotiation. This does not 1228 preclude an authentication mechanism such as EXTERNAL (defined in 1229 [SASL]) from using client identity determined by the [TLS] 1230 negotiation. 1232 Once [TLS] has been started, the client MUST discard cached 1233 information about server capabilities and SHOULD re-issue the 1234 CAPABILITY command. This is necessary to protect against man-in- 1235 the-middle attacks which alter the capabilities list prior to 1236 STARTTLS. The server MAY advertise different capabilities, and in 1237 particular SHOULD NOT advertise the STARTTLS capability, after a 1238 successful STARTTLS command. 1240 Example: C: a001 CAPABILITY 1241 S: * CAPABILITY IMAP4rev2 STARTTLS LOGINDISABLED 1242 S: a001 OK CAPABILITY completed 1243 C: a002 STARTTLS 1244 S: a002 OK Begin TLS negotiation now 1245 1246 C: a003 CAPABILITY 1247 S: * CAPABILITY IMAP4rev2 AUTH=PLAIN 1248 S: a003 OK CAPABILITY completed 1249 C: a004 LOGIN joe password 1250 S: a004 OK LOGIN completed 1252 6.2.2. AUTHENTICATE Command 1254 Arguments: SASL authentication mechanism name 1255 OPTIONAL initial response 1257 Responses: continuation data can be requested 1259 Result: OK - authenticate completed, now in authenticated state 1260 NO - authenticate failure: unsupported authentication 1261 mechanism, credentials rejected 1262 BAD - command unknown or arguments invalid, 1263 authentication exchange cancelled 1265 The AUTHENTICATE command indicates a [SASL] authentication mechanism 1266 to the server. If the server supports the requested authentication 1267 mechanism, it performs an authentication protocol exchange to 1268 authenticate and identify the client. It MAY also negotiate an 1269 OPTIONAL security layer for subsequent protocol interactions. If the 1270 requested authentication mechanism is not supported, the server 1271 SHOULD reject the AUTHENTICATE command by sending a tagged NO 1272 response. 1274 The AUTHENTICATE command supports the optional "initial response" 1275 feature defined in Section 5.1 of [SASL]. The client doesn't need to 1276 use it. If a SASL mechanism supports "initial response", but it is 1277 not specified by the client, the server handles this as specified in 1278 Section 3 of [SASL]. 1280 The service name specified by this protocol's profile of [SASL] is 1281 "imap". 1283 The authentication protocol exchange consists of a series of server 1284 challenges and client responses that are specific to the 1285 authentication mechanism. A server challenge consists of a command 1286 continuation request response with the "+" token followed by a BASE64 1287 encoded (see Section 4 of [RFC4648]) string. The client response 1288 consists of a single line consisting of a BASE64 encoded string. If 1289 the client wishes to cancel an authentication exchange, it issues a 1290 line consisting of a single "*". If the server receives such a 1291 response, or if it receives an invalid BASE64 string (e.g. 1292 characters outside the BASE64 alphabet, or non-terminal "="), it MUST 1293 reject the AUTHENTICATE command by sending a tagged BAD response. 1295 As with any other client response, this initial response MUST be 1296 encoded as BASE64. It also MUST be transmitted outside of a quoted 1297 string or literal. To send a zero-length initial response, the 1298 client MUST send a single pad character ("="). This indicates that 1299 the response is present, but is a zero-length string. 1301 When decoding the BASE64 data in the initial response, decoding 1302 errors MUST be treated as in any normal SASL client response, i.e. 1303 with a tagged BAD response. In particular, the server should check 1304 for any characters not explicitly allowed by the BASE64 alphabet, as 1305 well as any sequence of BASE64 characters that contains the pad 1306 character ('=') anywhere other than the end of the string (e.g., 1307 "=AAA" and "AAA=BBB" are not allowed). 1309 If the client uses an initial response with a SASL mechanism that 1310 does not support an initial response, the server MUST reject the 1311 command with a tagged BAD response. 1313 If a security layer is negotiated through the [SASL] authentication 1314 exchange, it takes effect immediately following the CRLF that 1315 concludes the authentication exchange for the client, and the CRLF of 1316 the tagged OK response for the server. 1318 While client and server implementations MUST implement the 1319 AUTHENTICATE command itself, it is not required to implement any 1320 authentication mechanisms other than the PLAIN mechanism described in 1321 [PLAIN]. Also, an authentication mechanism is not required to 1322 support any security layers. 1324 Note: a server implementation MUST implement a configuration in 1325 which it does NOT permit any plaintext password mechanisms, unless 1326 either the STARTTLS command has been negotiated or some other 1327 mechanism that protects the session from password snooping has 1328 been provided. Server sites SHOULD NOT use any configuration 1329 which permits a plaintext password mechanism without such a 1330 protection mechanism against password snooping. Client and server 1331 implementations SHOULD implement additional [SASL] mechanisms that 1332 do not use plaintext passwords, such the GSSAPI mechanism 1333 described in [SASL] and/or the SCRAM-SHA-256/SCRAM-SHA-256-PLUS 1334 [SCRAM-SHA-256] mechanisms. 1336 Servers and clients can support multiple authentication mechanisms. 1337 The server SHOULD list its supported authentication mechanisms in the 1338 response to the CAPABILITY command so that the client knows which 1339 authentication mechanisms to use. 1341 A server MAY include a CAPABILITY response code in the tagged OK 1342 response of a successful AUTHENTICATE command in order to send 1343 capabilities automatically. It is unnecessary for a client to send a 1344 separate CAPABILITY command if it recognizes these automatic 1345 capabilities. This should only be done if a security layer was not 1346 negotiated by the AUTHENTICATE command, because the tagged OK 1347 response as part of an AUTHENTICATE command is not protected by 1348 encryption/integrity checking. [SASL] requires the client to re- 1349 issue a CAPABILITY command in this case. The server MAY advertise 1350 different capabilities after a successful AUTHENTICATE command. 1352 If an AUTHENTICATE command fails with a NO response, the client MAY 1353 try another authentication mechanism by issuing another AUTHENTICATE 1354 command. It MAY also attempt to authenticate by using the LOGIN 1355 command (see Section 6.2.3 for more detail). In other words, the 1356 client MAY request authentication types in decreasing order of 1357 preference, with the LOGIN command as a last resort. 1359 The authorization identity passed from the client to the server 1360 during the authentication exchange is interpreted by the server as 1361 the user name whose privileges the client is requesting. 1363 Example: S: * OK IMAP4rev2 Server 1364 C: A001 AUTHENTICATE GSSAPI 1365 S: + 1366 C: YIIB+wYJKoZIhvcSAQICAQBuggHqMIIB5qADAgEFoQMCAQ6iBw 1367 MFACAAAACjggEmYYIBIjCCAR6gAwIBBaESGxB1Lndhc2hpbmd0 1368 b24uZWR1oi0wK6ADAgEDoSQwIhsEaW1hcBsac2hpdmFtcy5jYW 1369 Mud2FzaGluZ3Rvbi5lZHWjgdMwgdCgAwIBAaEDAgEDooHDBIHA 1370 cS1GSa5b+fXnPZNmXB9SjL8Ollj2SKyb+3S0iXMljen/jNkpJX 1371 AleKTz6BQPzj8duz8EtoOuNfKgweViyn/9B9bccy1uuAE2HI0y 1372 C/PHXNNU9ZrBziJ8Lm0tTNc98kUpjXnHZhsMcz5Mx2GR6dGknb 1373 I0iaGcRerMUsWOuBmKKKRmVMMdR9T3EZdpqsBd7jZCNMWotjhi 1374 vd5zovQlFqQ2Wjc2+y46vKP/iXxWIuQJuDiisyXF0Y8+5GTpAL 1375 pHDc1/pIGmMIGjoAMCAQGigZsEgZg2on5mSuxoDHEA1w9bcW9n 1376 FdFxDKpdrQhVGVRDIzcCMCTzvUboqb5KjY1NJKJsfjRQiBYBdE 1377 NKfzK+g5DlV8nrw81uOcP8NOQCLR5XkoMHC0Dr/80ziQzbNqhx 1378 O6652Npft0LQwJvenwDI13YxpwOdMXzkWZN/XrEqOWp6GCgXTB 1379 vCyLWLlWnbaUkZdEYbKHBPjd8t/1x5Yg== 1380 S: + YGgGCSqGSIb3EgECAgIAb1kwV6ADAgEFoQMCAQ+iSzBJoAMC 1381 AQGiQgRAtHTEuOP2BXb9sBYFR4SJlDZxmg39IxmRBOhXRKdDA0 1382 uHTCOT9Bq3OsUTXUlk0CsFLoa8j+gvGDlgHuqzWHPSQg== 1383 C: 1384 S: + YDMGCSqGSIb3EgECAgIBAAD/////6jcyG4GE3KkTzBeBiVHe 1385 ceP2CWY0SR0fAQAgAAQEBAQ= 1386 C: YDMGCSqGSIb3EgECAgIBAAD/////3LQBHXTpFfZgrejpLlLImP 1387 wkhbfa2QteAQAgAG1yYwE= 1388 S: A001 OK GSSAPI authentication successful 1390 Note: The line breaks within server challenges and client responses 1391 are for editorial clarity and are not in real authenticators. 1393 6.2.3. LOGIN Command 1395 Arguments: user name 1396 password 1398 Responses: no specific responses for this command 1400 Result: OK - login completed, now in authenticated state 1401 NO - login failure: user name or password rejected 1402 BAD - command unknown or arguments invalid 1404 The LOGIN command identifies the client to the server and carries the 1405 plaintext password authenticating this user. 1407 A server MAY include a CAPABILITY response code in the tagged OK 1408 response to a successful LOGIN command in order to send capabilities 1409 automatically. It is unnecessary for a client to send a separate 1410 CAPABILITY command if it recognizes these automatic capabilities. 1412 Example: C: a001 LOGIN SMITH SESAME 1413 S: a001 OK LOGIN completed 1415 Note: Use of the LOGIN command over an insecure network (such as the 1416 Internet) is a security risk, because anyone monitoring network 1417 traffic can obtain plaintext passwords. The LOGIN command SHOULD NOT 1418 be used except as a last resort, and it is recommended that client 1419 implementations have a means to disable any automatic use of the 1420 LOGIN command. 1422 Unless either the client is accessing IMAP service on IMAPS port 1423 [RFC8314], the STARTTLS command has been negotiated or some other 1424 mechanism that protects the session from password snooping has been 1425 provided, a server implementation MUST implement a configuration in 1426 which it advertises the LOGINDISABLED capability and does NOT permit 1427 the LOGIN command. Server sites SHOULD NOT use any configuration 1428 which permits the LOGIN command without such a protection mechanism 1429 against password snooping. A client implementation MUST NOT send a 1430 LOGIN command if the LOGINDISABLED capability is advertised. 1432 6.3. Client Commands - Authenticated State 1434 In the authenticated state, commands that manipulate mailboxes as 1435 atomic entities are permitted. Of these commands, the SELECT and 1436 EXAMINE commands will select a mailbox for access and enter the 1437 selected state. 1439 In addition to the universal commands (CAPABILITY, NOOP, and LOGOUT), 1440 the following commands are valid in the authenticated state: ENABLE, 1441 SELECT, EXAMINE, NAMESPACE, CREATE, DELETE, RENAME, SUBSCRIBE, 1442 UNSUBSCRIBE, LIST, LSUB, STATUS, APPEND and IDLE. 1444 6.3.1. ENABLE Command 1446 Arguments: capability names 1448 Responses: no specific responses for this command 1450 Result: OK - Relevant capabilities enabled 1451 BAD - No arguments, or syntax error in an argument 1453 Several IMAP extensions allow the server to return unsolicited 1454 responses specific to these extensions in certain circumstances. 1455 However, servers cannot send those unsolicited responses (with the 1456 exception of response codes (see Section 7.1) included in tagged or 1457 untagged OK/NO/BAD responses, which can always be sent) until they 1458 know that the clients support such extensions and thus won't choke on 1459 the extension response data. 1461 The ENABLE command provides an explicit indication from the client 1462 that it supports particular extensions. 1464 The ENABLE command takes a list of capability names, and requests the 1465 server to enable the named extensions. Once enabled using ENABLE, 1466 each extension remains active until the IMAP connection is closed. 1467 For each argument, the server does the following: 1469 o If the argument is not an extension known to the server, the 1470 server MUST ignore the argument. 1472 o If the argument is an extension known to the server, and it is not 1473 specifically permitted to be enabled using ENABLE, the server MUST 1474 ignore the argument. (Note that knowing about an extension 1475 doesn't necessarily imply supporting that extension.) 1477 o If the argument is an extension that is supported by the server 1478 and that needs to be enabled, the server MUST enable the extension 1479 for the duration of the connection. Note that once an extension 1480 is enabled, there is no way to disable it. 1482 If the ENABLE command is successful, the server MUST send an untagged 1483 ENABLED response Section 7.2.1. 1485 Clients SHOULD only include extensions that need to be enabled by the 1486 server. For example, a client can enable IMAP4rev2 specific 1487 behaviour when both IMAP4rev1 and IMAP4rev2 are advertised in the 1488 CAPABILITY response. Future RFCs may add to this list. 1490 The ENABLE command is only valid in the authenticated state, before 1491 any mailbox is selected. Clients MUST NOT issue ENABLE once they 1492 SELECT/EXAMINE a mailbox; however, server implementations don't have 1493 to check that no mailbox is selected or was previously selected 1494 during the duration of a connection. 1496 The ENABLE command can be issued multiple times in a session. It is 1497 additive; i.e., "ENABLE a b", followed by "ENABLE c" is the same as a 1498 single command "ENABLE a b c". When multiple ENABLE commands are 1499 issued, each corresponding ENABLED response SHOULD only contain 1500 extensions enabled by the corresponding ENABLE command. 1502 There are no limitations on pipelining ENABLE. For example, it is 1503 possible to send ENABLE and then immediately SELECT, or a LOGIN 1504 immediately followed by ENABLE. 1506 The server MUST NOT change the CAPABILITY list as a result of 1507 executing ENABLE; i.e., a CAPABILITY command issued right after an 1508 ENABLE command MUST list the same capabilities as a CAPABILITY 1509 command issued before the ENABLE command. This is demonstrated in 1510 the following example: 1512 C: t1 CAPABILITY 1513 S: * CAPABILITY IMAP4rev1 ID LITERAL+ ENABLE X-GOOD-IDEA 1514 S: t1 OK foo 1515 C: t2 ENABLE CONDSTORE X-GOOD-IDEA 1516 S: * ENABLED X-GOOD-IDEA 1517 S: t2 OK foo 1518 C: t3 CAPABILITY 1519 S: * CAPABILITY IMAP4rev1 ID LITERAL+ ENABLE X-GOOD-IDEA 1520 S: t3 OK foo again 1522 In the following example, the client enables CONDSTORE: 1524 C: a1 ENABLE CONDSTORE 1525 S: * ENABLED CONDSTORE 1526 S: a1 OK Conditional Store enabled 1528 6.3.1.1. Note to Designers of Extensions That May Use the ENABLE 1529 Command 1531 Designers of IMAP extensions are discouraged from creating extensions 1532 that require ENABLE unless there is no good alternative design. 1533 Specifically, extensions that cause potentially incompatible behavior 1534 changes to deployed server responses (and thus benefit from ENABLE) 1535 have a higher complexity cost than extensions that do not. 1537 6.3.2. SELECT Command 1539 Arguments: mailbox name 1541 Responses: REQUIRED untagged responses: FLAGS, EXISTS 1542 REQUIRED OK untagged responses: PERMANENTFLAGS, 1543 UIDNEXT, UIDVALIDITY 1545 Result: OK - select completed, now in selected state 1546 NO - select failure, now in authenticated state: no 1547 such mailbox, can't access mailbox 1548 BAD - command unknown or arguments invalid 1550 The SELECT command selects a mailbox so that messages in the mailbox 1551 can be accessed. Before returning an OK to the client, the server 1552 MUST send the following untagged data to the client. Note that 1553 earlier versions of this protocol only required the FLAGS and EXISTS 1554 untagged data; consequently, client implementations SHOULD implement 1555 default behavior for missing data as discussed with the individual 1556 item. 1558 FLAGS Defined flags in the mailbox. See the description of the 1559 FLAGS response for more detail. 1561 EXISTS The number of messages in the mailbox. See the 1562 description of the EXISTS response for more detail. 1564 OK [PERMANENTFLAGS ()] A list of message flags that 1565 the client can change permanently. If this is missing, the client 1566 should assume that all flags can be changed permanently. 1568 OK [UIDNEXT ] The next unique identifier value. Refer to 1569 Section 2.3.1.1 for more information. If this is missing, the 1570 client can not make any assumptions about the next unique 1571 identifier value. 1573 OK [UIDVALIDITY ] The unique identifier validity value. Refer to 1574 Section 2.3.1.1 for more information. If this is missing, the 1575 server does not support unique identifiers. 1577 Only one mailbox can be selected at a time in a connection; 1578 simultaneous access to multiple mailboxes requires multiple 1579 connections. The SELECT command automatically deselects any 1580 currently selected mailbox before attempting the new selection. 1581 Consequently, if a mailbox is selected and a SELECT command that 1582 fails is attempted, no mailbox is selected. When deselecting a 1583 selected mailbox, the server MUST return an untagged OK response with 1584 the "[CLOSED]" response code when the currently selected mailbox is 1585 closed (see Paragraph 10). 1587 If the client is permitted to modify the mailbox, the server SHOULD 1588 prefix the text of the tagged OK response with the "[READ-WRITE]" 1589 response code. 1591 If the client is not permitted to modify the mailbox but is permitted 1592 read access, the mailbox is selected as read-only, and the server 1593 MUST prefix the text of the tagged OK response to SELECT with the 1594 "[READ-ONLY]" response code. Read-only access through SELECT differs 1595 from the EXAMINE command in that certain read-only mailboxes MAY 1596 permit the change of permanent state on a per-user (as opposed to 1597 global) basis. Netnews messages marked in a server-based .newsrc 1598 file are an example of such per-user permanent state that can be 1599 modified with read-only mailboxes. 1601 Example: C: A142 SELECT INBOX 1602 S: * 172 EXISTS 1603 S: * OK [UIDVALIDITY 3857529045] UIDs valid 1604 S: * OK [UIDNEXT 4392] Predicted next UID 1605 S: * FLAGS (\Answered \Flagged \Deleted \Seen \Draft) 1606 S: * OK [PERMANENTFLAGS (\Deleted \Seen \*)] Limited 1607 S: A142 OK [READ-WRITE] SELECT completed 1609 6.3.3. EXAMINE Command 1611 Arguments: mailbox name 1613 Responses: REQUIRED untagged responses: FLAGS, EXISTS 1614 REQUIRED OK untagged responses: PERMANENTFLAGS, 1615 UIDNEXT, UIDVALIDITY 1617 Result: OK - examine completed, now in selected state 1618 NO - examine failure, now in authenticated state: no 1619 such mailbox, can't access mailbox BAD - command unknown 1620 or arguments invalid 1622 The EXAMINE command is identical to SELECT and returns the same 1623 output; however, the selected mailbox is identified as read-only. No 1624 changes to the permanent state of the mailbox, including per-user 1625 state, are permitted. 1627 The text of the tagged OK response to the EXAMINE command MUST begin 1628 with the "[READ-ONLY]" response code. 1630 Example: C: A932 EXAMINE blurdybloop 1631 S: * 17 EXISTS 1632 S: * OK [UIDVALIDITY 3857529045] UIDs valid 1633 S: * OK [UIDNEXT 4392] Predicted next UID 1634 S: * FLAGS (\Answered \Flagged \Deleted \Seen \Draft) 1635 S: * OK [PERMANENTFLAGS ()] No permanent flags permitted 1636 S: A932 OK [READ-ONLY] EXAMINE completed 1638 6.3.4. CREATE Command 1640 Arguments: mailbox name 1642 Responses: no specific responses for this command 1644 Result: OK - create completed 1645 NO - create failure: can't create mailbox with that name 1646 BAD - command unknown or arguments invalid 1648 The CREATE command creates a mailbox with the given name. An OK 1649 response is returned only if a new mailbox with that name has been 1650 created. It is an error to attempt to create INBOX or a mailbox with 1651 a name that refers to an extant mailbox. Any error in creation will 1652 return a tagged NO response. If a client attempts to create a UTF-8 1653 mailbox name that is not a valid Net-Unicode name, the server MUST 1654 reject the creation or convert the name to Net-Unicode prior to 1655 creating the mailbox. 1657 If the mailbox name is suffixed with the server's hierarchy separator 1658 character (as returned from the server by a LIST command), this is a 1659 declaration that the client intends to create mailbox names under 1660 this name in the hierarchy. Server implementations that do not 1661 require this declaration MUST ignore the declaration. In any case, 1662 the name created is without the trailing hierarchy delimiter. 1664 If the server's hierarchy separator character appears elsewhere in 1665 the name, the server SHOULD create any superior hierarchical names 1666 that are needed for the CREATE command to be successfully completed. 1667 In other words, an attempt to create "foo/bar/zap" on a server in 1668 which "/" is the hierarchy separator character SHOULD create foo/ and 1669 foo/bar/ if they do not already exist. 1671 If a new mailbox is created with the same name as a mailbox which was 1672 deleted, its unique identifiers MUST be greater than any unique 1673 identifiers used in the previous incarnation of the mailbox UNLESS 1674 the new incarnation has a different unique identifier validity value. 1675 See the description of the UID command for more detail. 1677 Example: C: A003 CREATE owatagusiam/ 1678 S: A003 OK CREATE completed 1679 C: A004 CREATE owatagusiam/blurdybloop 1680 S: A004 OK CREATE completed 1682 Note: The interpretation of this example depends on whether "/" 1683 was returned as the hierarchy separator from LIST. If "/" is the 1684 hierarchy separator, a new level of hierarchy named "owatagusiam" 1685 with a member called "blurdybloop" is created. Otherwise, two 1686 mailboxes at the same hierarchy level are created. 1688 6.3.5. DELETE Command 1690 Arguments: mailbox name 1692 Responses: no specific responses for this command 1694 Result: OK - delete completed 1695 NO - delete failure: can't delete mailbox with that name 1696 BAD - command unknown or arguments invalid 1698 The DELETE command permanently removes the mailbox with the given 1699 name. A tagged OK response is returned only if the mailbox has been 1700 deleted. It is an error to attempt to delete INBOX or a mailbox name 1701 that does not exist. 1703 The DELETE command MUST NOT remove inferior hierarchical names. For 1704 example, if a mailbox "foo" has an inferior "foo.bar" (assuming "." 1705 is the hierarchy delimiter character), removing "foo" MUST NOT remove 1706 "foo.bar". It is an error to attempt to delete a name that has 1707 inferior hierarchical names and also has the \Noselect mailbox name 1708 attribute (see the description of the LIST response for more 1709 details). 1711 It is permitted to delete a name that has inferior hierarchical names 1712 and does not have the \Noselect mailbox name attribute. If the 1713 server implementation does not permit deleting the name while 1714 inferior hierarchical names exists the \Noselect mailbox name 1715 attribute is set for that name. In any case, all messages in that 1716 mailbox are removed by the DELETE command. 1718 The value of the highest-used unique identifier of the deleted 1719 mailbox MUST be preserved so that a new mailbox created with the same 1720 name will not reuse the identifiers of the former incarnation, UNLESS 1721 the new incarnation has a different unique identifier validity value. 1722 See the description of the UID command for more detail. 1724 Examples: C: A682 LIST "" * 1725 S: * LIST () "/" blurdybloop 1726 S: * LIST (\Noselect) "/" foo 1727 S: * LIST () "/" foo/bar 1728 S: A682 OK LIST completed 1729 C: A683 DELETE blurdybloop 1730 S: A683 OK DELETE completed 1731 C: A684 DELETE foo 1732 S: A684 NO Name "foo" has inferior hierarchical names 1733 C: A685 DELETE foo/bar 1734 S: A685 OK DELETE Completed 1735 C: A686 LIST "" * 1736 S: * LIST (\Noselect) "/" foo 1737 S: A686 OK LIST completed 1738 C: A687 DELETE foo 1739 S: A687 OK DELETE Completed 1740 C: A82 LIST "" * 1741 S: * LIST () "." blurdybloop 1742 S: * LIST () "." foo 1743 S: * LIST () "." foo.bar 1744 S: A82 OK LIST completed 1745 C: A83 DELETE blurdybloop 1746 S: A83 OK DELETE completed 1747 C: A84 DELETE foo 1748 S: A84 OK DELETE Completed 1749 C: A85 LIST "" * 1750 S: * LIST () "." foo.bar 1751 S: A85 OK LIST completed 1752 C: A86 LIST "" % 1753 S: * LIST (\Noselect) "." foo 1754 S: A86 OK LIST completed 1756 6.3.6. RENAME Command 1758 Arguments: existing mailbox name 1759 new mailbox name 1761 Responses: no specific responses for this command 1763 Result: OK - rename completed 1764 NO - rename failure: can't rename mailbox with that name, 1765 can't rename to mailbox with that name 1766 BAD - command unknown or arguments invalid 1768 The RENAME command changes the name of a mailbox. A tagged OK 1769 response is returned only if the mailbox has been renamed. It is an 1770 error to attempt to rename from a mailbox name that does not exist or 1771 to a mailbox name that already exists. Any error in renaming will 1772 return a tagged NO response. 1774 If the name has inferior hierarchical names, then the inferior 1775 hierarchical names MUST also be renamed. For example, a rename of 1776 "foo" to "zap" will rename "foo/bar" (assuming "/" is the hierarchy 1777 delimiter character) to "zap/bar". 1779 If the server's hierarchy separator character appears in the name, 1780 the server SHOULD create any superior hierarchical names that are 1781 needed for the RENAME command to complete successfully. In other 1782 words, an attempt to rename "foo/bar/zap" to baz/rag/zowie on a 1783 server in which "/" is the hierarchy separator character SHOULD 1784 create baz/ and baz/rag/ if they do not already exist. 1786 The value of the highest-used unique identifier of the old mailbox 1787 name MUST be preserved so that a new mailbox created with the same 1788 name will not reuse the identifiers of the former incarnation, UNLESS 1789 the new incarnation has a different unique identifier validity value. 1790 See the description of the UID command for more detail. 1792 Renaming INBOX is permitted, and has special behavior. It moves all 1793 messages in INBOX to a new mailbox with the given name, leaving INBOX 1794 empty. If the server implementation supports inferior hierarchical 1795 names of INBOX, these are unaffected by a rename of INBOX. 1797 Examples: C: A682 LIST "" * 1798 S: * LIST () "/" blurdybloop 1799 S: * LIST (\Noselect) "/" foo 1800 S: * LIST () "/" foo/bar 1801 S: A682 OK LIST completed 1802 C: A683 RENAME blurdybloop sarasoop 1803 S: A683 OK RENAME completed 1804 C: A684 RENAME foo zowie 1805 S: A684 OK RENAME Completed 1806 C: A685 LIST "" * 1807 S: * LIST () "/" sarasoop 1808 S: * LIST (\Noselect) "/" zowie 1809 S: * LIST () "/" zowie/bar 1810 S: A685 OK LIST completed 1812 C: Z432 LIST "" * 1813 S: * LIST () "." INBOX 1814 S: * LIST () "." INBOX.bar 1815 S: Z432 OK LIST completed 1816 C: Z433 RENAME INBOX old-mail 1817 S: Z433 OK RENAME completed 1818 C: Z434 LIST "" * 1819 S: * LIST () "." INBOX 1820 S: * LIST () "." INBOX.bar 1821 S: * LIST () "." old-mail 1822 S: Z434 OK LIST completed 1824 6.3.7. SUBSCRIBE Command 1826 Arguments: mailbox 1828 Responses: no specific responses for this command 1830 Result: OK - subscribe completed 1831 NO - subscribe failure: can't subscribe to that name 1832 BAD - command unknown or arguments invalid 1834 The SUBSCRIBE command adds the specified mailbox name to the server's 1835 set of "active" or "subscribed" mailboxes as returned by the LSUB 1836 command. This command returns a tagged OK response only if the 1837 subscription is successful. 1839 A server MAY validate the mailbox argument to SUBSCRIBE to verify 1840 that it exists. However, it MUST NOT unilaterally remove an existing 1841 mailbox name from the subscription list even if a mailbox by that 1842 name no longer exists. 1844 Note: This requirement is because a server site can choose to 1845 routinely remove a mailbox with a well-known name (e.g., "system- 1846 alerts") after its contents expire, with the intention of 1847 recreating it when new contents are appropriate. 1849 Example: C: A002 SUBSCRIBE #news.comp.mail.mime 1850 S: A002 OK SUBSCRIBE completed 1852 6.3.8. UNSUBSCRIBE Command 1854 Arguments: mailbox name 1856 Responses: no specific responses for this command 1858 Result: OK - unsubscribe completed 1859 NO - unsubscribe failure: can't unsubscribe that name 1860 BAD - command unknown or arguments invalid 1862 The UNSUBSCRIBE command removes the specified mailbox name from the 1863 server's set of "active" or "subscribed" mailboxes as returned by the 1864 LSUB command. This command returns a tagged OK response only if the 1865 unsubscription is successful. 1867 Example: C: A002 UNSUBSCRIBE #news.comp.mail.mime 1868 S: A002 OK UNSUBSCRIBE completed 1870 6.3.9. LIST Command 1872 Arguments (basic): reference name 1873 mailbox name with possible wildcards 1875 Arguments (extended): selection options (OPTIONAL) 1876 reference name 1877 mailbox patterns 1878 return options (OPTIONAL) 1880 Responses: untagged responses: LIST 1882 Result: OK - list completed 1883 NO - list failure: can't list that reference or name 1884 BAD - command unknown or arguments invalid 1886 THIS VERSION HAS ONLY AN INITIAL PASS AT ADDING THE EXTENDED LIST 1887 SYNTAX AND OPTIONS. THERE'S STILL A GOOD DEAL OR WORK TO DO ON IT, 1888 AND THE ABNF IS NOT THERE YET. 1890 The LIST command returns a subset of names from the complete set of 1891 all names available to the client. Zero or more untagged LIST 1892 replies are returned, containing the name attributes, hierarchy 1893 delimiter, name, and possible extension information; see the 1894 description of the LIST reply for more detail. 1896 The LIST command SHOULD return its data quickly, without undue delay. 1897 For example, it SHOULD NOT go to excess trouble to calculate the 1898 \Marked or \Unmarked status or perform other processing; if each name 1899 requires 1 second of processing, then a list of 1200 names would take 1900 20 minutes! 1902 The extended LIST command, originally introduced in [RFC5258], 1903 provides capabilities beyond that of the original IMAP LIST command. 1904 The extended syntax is being used if one of the following conditions 1905 is true: 1907 1. if the first word after the command name begins with a 1908 parenthesis ("LIST selection options") 1910 2. if the second word after the command name begins with a 1911 parenthesis ("multiple mailbox patterns") 1913 3. if the LIST command has more than 2 parameters ("LIST return 1914 options") 1916 An empty ("" string) reference name argument indicates that the 1917 mailbox name is interpreted as by SELECT. The returned mailbox names 1918 MUST match the supplied mailbox name pattern(s). A non-empty 1919 reference name argument is the name of a mailbox or a level of 1920 mailbox hierarchy, and indicates the context in which the mailbox 1921 name is interpreted. Clients SHOULD use the empty reference 1922 argument. 1924 In the basic syntax only, an empty ("" string) mailbox name argument 1925 is a special request to return the hierarchy delimiter and the root 1926 name of the name given in the reference. The value returned as the 1927 root MAY be the empty string if the reference is non-rooted or is an 1928 empty string. In all cases, a hierarchy delimiter (or NIL if there 1929 is no hierarchy) is returned. This permits a client to get the 1930 hierarchy delimiter (or find out that the mailbox names are flat) 1931 even when no mailboxes by that name currently exist. 1933 In the extended syntax, any mailbox name arguments that are empty 1934 strings are ignored. There is no special meaning for empty mailbox 1935 names when the extended syntax is used. 1937 The reference and mailbox name arguments are interpreted into a 1938 canonical form that represents an unambiguous left-to-right 1939 hierarchy. The returned mailbox names will be in the interpreted 1940 form. 1942 Note: The interpretation of the reference argument is 1943 implementation-defined. It depends upon whether the server 1944 implementation has a concept of the "current working directory" 1945 and leading "break out characters", which override the current 1946 working directory. 1948 For example, on a server which exports a UNIX or NT filesystem, 1949 the reference argument contains the current working directory, and 1950 the mailbox name argument would contain the name as interpreted in 1951 the current working directory. 1953 If a server implementation has no concept of break out characters, 1954 the canonical form is normally the reference name appended with 1955 the mailbox name. Note that if the server implements the 1956 namespace convention (Section 5.1.2.1), "#" is a break out 1957 character and must be treated as such. 1959 If the reference argument is not a level of mailbox hierarchy 1960 (that is, it is a \NoInferiors name), and/or the reference 1961 argument does not end with the hierarchy delimiter, it is 1962 implementation-dependent how this is interpreted. For example, a 1963 reference of "foo/bar" and mailbox name of "rag/baz" could be 1964 interpreted as "foo/bar/rag/baz", "foo/barrag/baz", or "foo/rag/ 1965 baz". A client SHOULD NOT use such a reference argument except at 1966 the explicit request of the user. A hierarchical browser MUST NOT 1967 make any assumptions about server interpretation of the reference 1968 unless the reference is a level of mailbox hierarchy AND ends with 1969 the hierarchy delimiter. 1971 Any part of the reference argument that is included in the 1972 interpreted form SHOULD prefix the interpreted form. It SHOULD also 1973 be in the same form as the reference name argument. This rule 1974 permits the client to determine if the returned mailbox name is in 1975 the context of the reference argument, or if something about the 1976 mailbox argument overrode the reference argument. Without this rule, 1977 the client would have to have knowledge of the server's naming 1978 semantics including what characters are "breakouts" that override a 1979 naming context. 1981 For example, here are some examples of how references 1982 and mailbox names might be interpreted on a UNIX-based 1983 server: 1985 Reference Mailbox Name Interpretation 1986 ------------ ------------ -------------- 1987 ~smith/Mail/ foo.* ~smith/Mail/foo.* 1988 archive/ % archive/% 1989 #news. comp.mail.* #news.comp.mail.* 1990 ~smith/Mail/ /usr/doc/foo /usr/doc/foo 1991 archive/ ~fred/Mail/* ~fred/Mail/* 1993 The first three examples demonstrate interpretations in 1994 the context of the reference argument. Note that 1995 "~smith/Mail" SHOULD NOT be transformed into something 1996 like "/u2/users/smith/Mail", or it would be impossible 1997 for the client to determine that the interpretation was 1998 in the context of the reference. 2000 The character "*" is a wildcard, and matches zero or more characters 2001 at this position. The character "%" is similar to "*", but it does 2002 not match a hierarchy delimiter. If the "%" wildcard is the last 2003 character of a mailbox name argument, matching levels of hierarchy 2004 are also returned. If these levels of hierarchy are not also 2005 selectable mailboxes, they are returned with the \Noselect mailbox 2006 name attribute (see the description of the LIST response for more 2007 details). 2009 If multiple mailbox patterns are used (in the extended syntax), a 2010 mailbox matches if it matches at least one mailbox pattern. If a 2011 mailbox matches more than one pattern, it is still only returned 2012 once. Any syntactically valid pattern that is not accepted by a 2013 server for any reason MUST be silently ignored. 2015 Selection options tell the server to limit the mailbox names that are 2016 selected by the LIST operation. If selection options are used, the 2017 mailboxes returned are those that match both the list of mailbox 2018 patterns and the selection options. Unless a particular selection 2019 option provides special rules, the selection options are cumulative: 2020 a mailbox that matches the mailbox patterns is selected only if it 2021 also matches all of the selection options. (An example of a 2022 selection option with special rules is the RECURSIVEMATCH option.) 2024 Return options control what information is returned for each matched 2025 mailbox. Return options MUST NOT cause the server to report 2026 information about additional mailbox names other than those that 2027 match the patterns and selection options. If no return options are 2028 specified, the client is only expecting information about mailbox 2029 attributes. The server MAY return other information about the 2030 matched mailboxes, and clients MUST be able to handle that situation. 2032 Initial selection options and return options are defined in the 2033 following subsections, and new ones will also be defined in 2034 extensions. Initial options MUST be supported. Each non-initial 2035 option will be enabled by a capability string (one capability may 2036 enable multiple options), and a client MUST NOT send an option for 2037 which the server has not advertised support. A server MUST respond 2038 to options it does not recognize with a BAD response. The client 2039 SHOULD NOT specify any option more than once; however, if the client 2040 does this, the server MUST act as if it received the option only 2041 once. The order in which options are specified by the client is not 2042 significant. 2044 In general, each selection option except RECURSIVEMATCH will have a 2045 corresponding return option. The REMOTE selection option is an 2046 anomaly in this regard, and does not have a corresponding return 2047 option. That is because it expands, rather than restricts, the set 2048 of mailboxes that are returned. Future extensions to this 2049 specification should keep parallelism in mind and define a pair of 2050 corresponding options. 2052 Server implementations are permitted to "hide" otherwise accessible 2053 mailboxes from the wildcard characters, by preventing certain 2054 characters or names from matching a wildcard in certain situations. 2055 For example, a UNIX-based server might restrict the interpretation of 2056 "*" so that an initial "/" character does not match. 2058 The special name INBOX is included in the output from LIST, if INBOX 2059 is supported by this server for this user and if the uppercase string 2060 "INBOX" matches the interpreted reference and mailbox name arguments 2061 with wildcards as described above. The criteria for omitting INBOX 2062 is whether SELECT INBOX will return failure; it is not relevant 2063 whether the user's real INBOX resides on this or some other server. 2065 6.3.9.1. LIST Selection Options 2067 The selection options defined in this specification are as follows: 2069 SUBSCRIBED - causes the LIST command to list subscribed names, 2070 rather than the existing mailboxes. This will often be a subset 2071 of the actual mailboxes. It's also possible for this list to 2072 contain the names of mailboxes that don't exist. In any case, the 2073 list MUST include exactly those mailbox names that match the 2074 canonical list pattern and are subscribed to. This option is 2075 intended to supplement the LSUB command. Of particular note are 2076 the mailbox attributes as returned by this option, compared with 2077 what is returned by LSUB. With the latter, the attributes 2078 returned may not reflect the actual attribute status on the 2079 mailbox name, and the \NoSelect attribute has a second special 2080 meaning (it indicates that this mailbox is not, itself, 2081 subscribed, but that it has descendant mailboxes that are). With 2082 the SUBSCRIBED selection option described here, the attributes are 2083 accurate and complete, and have no special meanings. "LSUB" and 2084 "LIST (SUBSCRIBED)" are, thus, not the same thing, and some 2085 servers must do significant extra work to respond to "LIST 2086 (SUBSCRIBED)". Because of this, clients SHOULD continue to use 2087 "LSUB" unless they specifically want the additional information 2088 offered by "LIST (SUBSCRIBED)". 2090 This option defines a new mailbox attribute, "\Subscribed", that 2091 indicates that a mailbox name is subscribed to. The "\Subscribed" 2092 attribute MUST be supported and MUST be accurately computed when 2093 the SUBSCRIBED selection option is specified. 2095 Note that the SUBSCRIBED selection option implies the SUBSCRIBED 2096 return option (see below). 2098 REMOTE - causes the LIST command to show remote mailboxes as well as 2099 local ones, as described in [RFC2193]. This option is intended to 2100 replace the RLIST command and, in conjunction with the SUBSCRIBED 2101 selection option, the RLSUB command. 2103 This option defines a new mailbox attribute, "\Remote", that 2104 indicates that a mailbox is a remote mailbox. The "\Remote" 2105 attribute MUST be accurately computed when the REMOTE option is 2106 specified. 2108 The REMOTE selection option has no interaction with other options. 2109 Its effect is to tell the server to apply the other options, if 2110 any, to remote mailboxes, in addition to local ones. In 2111 particular, it has no interaction with RECURSIVEMATCH (see below). 2112 A request for (REMOTE RECURSIVEMATCH) is invalid, because a 2113 request for (RECURSIVEMATCH) is. A request for (REMOTE 2114 RECURSIVEMATCH SUBSCRIBED) is asking for all subscribed mailboxes, 2115 both local and remote. 2117 RECURSIVEMATCH - this option forces the server to return information 2118 about parent mailboxes that don't match other selection options, 2119 but have some submailboxes that do. Information about children is 2120 returned in the CHILDINFO extended data item, as described in 2121 Section 6.3.9.5. 2123 Note 1: In order for a parent mailbox to be returned, it still has 2124 to match the canonical LIST pattern. 2126 Note 2: When returning the CHILDINFO extended data item, it 2127 doesn't matter whether or not the submailbox matches the canonical 2128 LIST pattern. See also example 9 in Section 6.3.9.6. 2130 The RECURSIVEMATCH option MUST NOT occur as the only selection 2131 option (or only with REMOTE), as it only makes sense when other 2132 selection options are also used. The server MUST return BAD 2133 tagged response in such case. 2135 Note that even if the RECURSIVEMATCH option is specified, the 2136 client MUST still be able to handle a case when a CHILDINFO 2137 extended data item is returned and there are no submailboxes that 2138 meet the selection criteria of the subsequent LIST command, as 2139 they can be deleted/renamed after the LIST response was sent, but 2140 before the client had a chance to access them. 2142 6.3.9.2. LIST Return Options 2144 The return options defined in this specification are as follows: 2146 SUBSCRIBED - causes the LIST command to return subscription state 2147 for all matching mailbox names. The "\Subscribed" attribute MUST 2148 be supported and MUST be accurately computed when the SUBSCRIBED 2149 return option is specified. Further, all mailbox flags MUST be 2150 accurately computed (this differs from the behavior of the LSUB 2151 command). 2153 CHILDREN - requests mailbox child information as originally proposed 2154 in [RFC3348]. See Section 6.3.9.4, below, for details. This 2155 option MUST be supported by all servers. 2157 6.3.9.3. General Principles for Returning LIST Responses 2159 This section outlines several principles that can be used by server 2160 implementations of this document to decide whether a LIST response 2161 should be returned, as well as how many responses and what kind of 2162 information they may contain. 2164 1. At most one LIST response should be returned for each mailbox 2165 name that matches the canonical LIST pattern. Server 2166 implementors must not assume that clients will be able to 2167 assemble mailbox attributes and other information returned in 2168 multiple LIST responses. 2170 2. There are only two reasons for including a matching mailbox name 2171 in the responses to the LIST command (note that the server is 2172 allowed to return unsolicited responses at any time, and such 2173 responses are not governed by this rule): 2175 A. The mailbox name also satisfies the selection criteria. 2177 B. The mailbox name doesn't satisfy the selection criteria, but 2178 it has at least one descendant mailbox name that satisfies 2179 the selection criteria and that doesn't match the canonical 2180 LIST pattern. 2182 For more information on this case, see the CHILDINFO extended 2183 data item described in Section 6.3.9.5. Note that the 2184 CHILDINFO extended data item can only be returned when the 2185 RECURSIVEMATCH selection option is specified. 2187 3. Attributes returned in the same LIST response must be treated 2188 additively. For example, the following response 2190 S: * LIST (\Subscribed \NonExistent) "/" "Fruit/Peach" 2192 means that the "Fruit/Peach" mailbox doesn't exist, but it is 2193 subscribed. 2195 6.3.9.4. The CHILDREN Return Option 2197 The CHILDREN return option implements the Child Mailbox Extension, 2198 originally proposed by Mike Gahrns and Raymond Cheng, of Microsoft 2199 Corporation. Most of the information in this section is taken 2200 directly from their original specification [RFC3348]. The CHILDREN 2201 return option is simply an indication that the client wants this 2202 information; a server MAY provide it even if the option is not 2203 specified. 2205 Many IMAP4 clients present to the user a hierarchical view of the 2206 mailboxes that a user has access to. Rather than initially 2207 presenting to the user the entire mailbox hierarchy, it is often 2208 preferable to show to the user a collapsed outline list of the 2209 mailbox hierarchy (particularly if there is a large number of 2210 mailboxes). The user can then expand the collapsed outline hierarchy 2211 as needed. It is common to include within the collapsed hierarchy a 2212 visual clue (such as a ''+'') to indicate that there are child 2213 mailboxes under a particular mailbox. When the visual clue is 2214 clicked, the hierarchy list is expanded to show the child mailboxes. 2215 The CHILDREN return option provides a mechanism for a client to 2216 efficiently determine whether a particular mailbox has children, 2217 without issuing a LIST "" * or a LIST "" % for each mailbox name. 2218 The CHILDREN return option defines two new attributes that MUST be 2219 returned within a LIST response: \HasChildren and \HasNoChildren. 2221 Although these attributes MAY be returned in response to any LIST 2222 command, the CHILDREN return option is provided to indicate that the 2223 client particularly wants this information. If the CHILDREN return 2224 option is present, the server MUST return these attributes even if 2225 their computation is expensive. 2227 \HasChildren 2229 The presence of this attribute indicates that the mailbox has 2230 child mailboxes. A server SHOULD NOT set this attribute if 2231 there are child mailboxes and the user does not have permission 2232 to access any of them. In this case, \HasNoChildren SHOULD be 2233 used. In many cases, however, a server may not be able to 2234 efficiently compute whether a user has access to any child 2235 mailbox. Note that even though the \HasChildren attribute for a 2236 mailbox must be correct at the time of processing of the 2237 mailbox, a client must be prepared to deal with a situation when 2238 a mailbox is marked with the \HasChildren attribute, but no 2239 child mailbox appears in the response to the LIST command. This 2240 might happen, for example, due to children mailboxes being 2241 deleted or made inaccessible to the user (using access control) 2242 by another client before the server is able to list them. 2244 \HasNoChildren 2246 The presence of this attribute indicates that the mailbox has NO 2247 child mailboxes that are accessible to the currently 2248 authenticated user. 2250 It is an error for the server to return both a \HasChildren and a 2251 \HasNoChildren attribute in the same LIST response. 2253 Note: the \HasNoChildren attribute should not be confused with the 2254 IMAP4 defined attribute \NoInferiors, which indicates that no child 2255 mailboxes exist now and none can be created in the future. 2257 6.3.9.5. CHILDINFO Extended Data Item 2259 The CHILDINFO extended data item MUST NOT be returned unless the 2260 client has specified the RECURSIVEMATCH selection option. 2262 The CHILDINFO extended data item in a LIST response describes the 2263 selection criteria that has caused it to be returned and indicates 2264 that the mailbox has at least one descendant mailbox that matches the 2265 selection criteria. 2267 The LSUB command indicates this condition by using the "\NoSelect" 2268 attribute, but the LIST (SUBSCRIBED) command MUST NOT do that, since 2269 "\NoSelect" retains its original meaning here. Further, the 2270 CHILDINFO extended data item is more general, in that it can be used 2271 with any extended set of selection criteria. 2273 Note: Some servers allow for mailboxes to exist without requiring 2274 their parent to exist. For example, a mailbox "Customers/ABC" can 2275 exist while the mailbox "Customers" does not. As CHILDINFO extended 2276 data item is not allowed if the RECURSIVEMATCH selection option is 2277 not specified, such servers SHOULD use the "\NonExistent 2278 \HasChildren" attribute pair to signal to the client that there is a 2279 descendant mailbox that matches the selection criteria. See example 2280 11 in Section 6.3.9.6. 2282 The returned selection criteria allow the client to distinguish a 2283 solicited response from an unsolicited one, as well as to distinguish 2284 among solicited responses caused by multiple pipelined LIST commands 2285 that specify different criteria. 2287 Servers SHOULD ONLY return a non-matching mailbox name along with 2288 CHILDINFO if at least one matching child is not also being returned. 2289 That is, servers SHOULD suppress redundant CHILDINFO responses. 2291 Examples 8 and 10 in Section 6.3.9.6 demonstrate the difference 2292 between present CHILDINFO extended data item and the "\HasChildren" 2293 attribute. 2295 The following table summarizes interaction between the "\NonExistent" 2296 attribute and CHILDINFO (the first column indicates whether the 2297 parent mailbox exists): 2299 +--------+--------------+--------------------+----------------------+ 2300 | exists | meets the | has a child that | returned LIST- | 2301 | | selection | meets the | EXTENDED attributes | 2302 | | criteria | selection criteria | and CHILDINFO | 2303 +--------+--------------+--------------------+----------------------+ 2304 | no | no | no | no LIST response | 2305 | | | | returned | 2306 | yes | no | no | no LIST response | 2307 | | | | returned | 2308 | no | yes | no | (\NonExistent | 2309 | | | | ) | 2310 | yes | yes | no | () | 2311 | no | no | yes | (\NonExistent) + | 2312 | | | | CHILDINFO | 2313 | yes | no | yes | () + CHILDINFO | 2314 | no | yes | yes | (\NonExistent | 2315 | | | | ) + CHILDINFO | 2316 | yes | yes | yes | () + CHILDINFO | 2317 +--------+--------------+--------------------+----------------------+ 2319 where is one or more attributes that correspond to the 2320 selection criteria; for example, for the SUBSCRIBED option the 2321 is \Subscribed. 2323 6.3.9.6. LIST Command Examples 2325 This example shows some uses of the basic LIST command: 2327 Example: C: A101 LIST "" "" 2328 S: * LIST (\Noselect) "/" "" 2329 S: A101 OK LIST Completed 2330 C: A102 LIST #news.comp.mail.misc "" 2331 S: * LIST (\Noselect) "." #news. 2332 S: A102 OK LIST Completed 2333 C: A103 LIST /usr/staff/jones "" 2334 S: * LIST (\Noselect) "/" / 2335 S: A103 OK LIST Completed 2336 C: A202 LIST ~/Mail/ % 2337 S: * LIST (\Noselect) "/" ~/Mail/foo 2338 S: * LIST () "/" ~/Mail/meetings 2339 S: A202 OK LIST completed 2341 Extended examples: 2343 1: The first example shows the complete local hierarchy that will 2344 be used for the other examples. 2346 C: A01 LIST "" "*" 2347 S: * LIST (\Marked \NoInferiors) "/" "inbox" 2348 S: * LIST () "/" "Fruit" 2349 S: * LIST () "/" "Fruit/Apple" 2350 S: * LIST () "/" "Fruit/Banana" 2351 S: * LIST () "/" "Tofu" 2352 S: * LIST () "/" "Vegetable" 2353 S: * LIST () "/" "Vegetable/Broccoli" 2354 S: * LIST () "/" "Vegetable/Corn" 2355 S: A01 OK done 2357 2: In the next example, we will see the subscribed mailboxes. This 2358 is similar to, but not equivalent with, . Note 2359 that the mailbox called "Fruit/Peach" is subscribed to, but does 2360 not actually exist (perhaps it was deleted while still 2361 subscribed). The "Fruit" mailbox is not subscribed to, but it 2362 has two subscribed children. The "Vegetable" mailbox is 2363 subscribed and has two children; one of them is subscribed as 2364 well. 2366 C: A02 LIST (SUBSCRIBED) "" "*" 2367 S: * LIST (\Marked \NoInferiors \Subscribed) "/" "inbox" 2368 S: * LIST (\Subscribed) "/" "Fruit/Banana" 2369 S: * LIST (\Subscribed \NonExistent) "/" "Fruit/Peach" 2370 S: * LIST (\Subscribed) "/" "Vegetable" 2371 S: * LIST (\Subscribed) "/" "Vegetable/Broccoli" 2372 S: A02 OK done 2374 3: The next example shows the use of the CHILDREN option. The 2375 client, without having to list the second level of hierarchy, 2376 now knows which of the top-level mailboxes have submailboxes 2377 (children) and which do not. Note that it's not necessary for 2378 the server to return the \HasNoChildren attribute for the inbox, 2379 because the \NoInferiors attribute already implies that, and has 2380 a stronger meaning. 2382 C: A03 LIST () "" "%" RETURN (CHILDREN) 2383 S: * LIST (\Marked \NoInferiors) "/" "inbox" 2384 S: * LIST (\HasChildren) "/" "Fruit" 2385 S: * LIST (\HasNoChildren) "/" "Tofu" 2386 S: * LIST (\HasChildren) "/" "Vegetable" 2387 S: A03 OK done 2389 4: In this example, we see more mailboxes that reside on another 2390 server. This is similar to the command . 2392 C: A04 LIST (REMOTE) "" "%" RETURN (CHILDREN) 2393 S: * LIST (\Marked \NoInferiors) "/" "inbox" 2394 S: * LIST (\HasChildren) "/" "Fruit" 2395 S: * LIST (\HasNoChildren) "/" "Tofu" 2396 S: * LIST (\HasChildren) "/" "Vegetable" 2397 S: * LIST (\Remote) "/" "Bread" 2398 S: * LIST (\HasChildren \Remote) "/" "Meat" 2399 S: A04 OK done 2401 5: The following example also requests the server to include 2402 mailboxes that reside on another server. The server returns 2403 information about all mailboxes that are subscribed. This is 2404 similar to the command . We also see the use of 2405 two selection options. 2407 C: A05 LIST (REMOTE SUBSCRIBED) "" "*" 2408 S: * LIST (\Marked \NoInferiors \Subscribed) "/" "inbox" 2409 S: * LIST (\Subscribed) "/" "Fruit/Banana" 2410 S: * LIST (\Subscribed \NonExistent) "/" "Fruit/Peach" 2411 S: * LIST (\Subscribed) "/" "Vegetable" 2412 S: * LIST (\Subscribed) "/" "Vegetable/Broccoli" 2413 S: * LIST (\Remote \Subscribed) "/" "Bread" 2414 S: A05 OK done 2416 6: The following example requests the server to include mailboxes 2417 that reside on another server. The server is asked to return 2418 subscription information for all returned mailboxes. This is 2419 different from the example above. 2421 Note that the output of this command is not a superset of the 2422 output in the previous example, as it doesn't include LIST 2423 response for the non-existent "Fruit/Peach". 2425 C: A06 LIST (REMOTE) "" "*" RETURN (SUBSCRIBED) 2426 S: * LIST (\Marked \NoInferiors \Subscribed) "/" "inbox" 2427 S: * LIST () "/" "Fruit" 2428 S: * LIST () "/" "Fruit/Apple" 2429 S: * LIST (\Subscribed) "/" "Fruit/Banana" 2430 S: * LIST () "/" "Tofu" 2431 S: * LIST (\Subscribed) "/" "Vegetable" 2432 S: * LIST (\Subscribed) "/" "Vegetable/Broccoli" 2433 S: * LIST () "/" "Vegetable/Corn" 2434 S: * LIST (\Remote \Subscribed) "/" "Bread" 2435 S: * LIST (\Remote) "/" "Meat" 2436 S: A06 OK done 2438 7: In the following example, the client has specified multiple 2439 mailbox patterns. Note that this example does not use the 2440 mailbox hierarchy used in the previous examples. 2442 C: BBB LIST "" ("INBOX" "Drafts" "Sent/%") 2443 S: * LIST () "/" "INBOX" 2444 S: * LIST (\NoInferiors) "/" "Drafts" 2445 S: * LIST () "/" "Sent/March2004" 2446 S: * LIST (\Marked) "/" "Sent/December2003" 2447 S: * LIST () "/" "Sent/August2004" 2448 S: BBB OK done 2450 8: The following example demonstrates the difference between the 2451 \HasChildren attribute and the CHILDINFO extended data item. 2453 Let's assume there is the following hierarchy: 2455 C: C01 LIST "" "*" 2456 S: * LIST (\Marked \NoInferiors) "/" "inbox" 2457 S: * LIST () "/" "Foo" 2458 S: * LIST () "/" "Foo/Bar" 2459 S: * LIST () "/" "Foo/Baz" 2460 S: * LIST () "/" "Moo" 2461 S: C01 OK done 2463 If the client asks RETURN (CHILDREN), it will get this: 2465 C: CA3 LIST "" "%" RETURN (CHILDREN) 2466 S: * LIST (\Marked \NoInferiors) "/" "inbox" 2467 S: * LIST (\HasChildren) "/" "Foo" 2468 S: * LIST (\HasNoChildren) "/" "Moo" 2469 S: CA3 OK done 2471 A) Let's also assume that the mailbox "Foo/Baz" is the only 2472 subscribed mailbox. Then we get this result: 2474 C: C02 LIST (SUBSCRIBED) "" "*" 2475 S: * LIST (\Subscribed) "/" "Foo/Baz" 2476 S: C02 OK done 2478 Now, if the client issues , the server 2479 will return no mailboxes (as the mailboxes "Moo", "Foo", and 2480 "Inbox" are NOT subscribed). However, if the client issues 2481 this: 2483 C: C04 LIST (SUBSCRIBED RECURSIVEMATCH) "" "%" 2484 S: * LIST () "/" "Foo" ("CHILDINFO" ("SUBSCRIBED")) 2485 S: C04 OK done 2486 (i.e., the mailbox "Foo" is not subscribed, but it has a child 2487 that is.) 2489 A1) If the mailbox "Foo" had also been subscribed, the last 2490 command would return this: 2492 C: C04 LIST (SUBSCRIBED RECURSIVEMATCH) "" "%" 2493 S: * LIST (\Subscribed) "/" "Foo" ("CHILDINFO" ("SUBSCRIBED")) 2494 S: C04 OK done 2496 or even this: 2498 C: C04 LIST (SUBSCRIBED RECURSIVEMATCH) "" "%" 2499 S: * LIST (\Subscribed \HasChildren) "/" "Foo" ("CHILDINFO" 2500 ("SUBSCRIBED")) 2501 S: C04 OK done 2503 A2) If we assume instead that the mailbox "Foo" is not part of 2504 the original hierarchy and is not subscribed, the last command 2505 will give this result: 2507 C: C04 LIST (SUBSCRIBED RECURSIVEMATCH) "" "%" 2508 S: * LIST (\NonExistent) "/" "Foo" ("CHILDINFO" ("SUBSCRIBED")) 2509 S: C04 OK done 2511 B) Now, let's assume that no mailbox is subscribed. In this 2512 case, the command will 2513 return no responses, as there are no subscribed children (even 2514 though "Foo" has children). 2516 C) And finally, suppose that only the mailboxes "Foo" and "Moo" 2517 are subscribed. In that case, we see this result: 2519 C: C04 LIST (SUBSCRIBED RECURSIVEMATCH) "" "%" RETURN (CHILDREN) 2520 S: * LIST (\HasChildren \Subscribed) "/" "Foo" 2521 S: * LIST (\HasNoChildren \Subscribed) "/" "Moo" 2522 S: C04 OK done 2524 (which means that the mailbox "Foo" has children, but none of 2525 them is subscribed). 2527 9: The following example demonstrates that the CHILDINFO extended 2528 data item is returned whether or not children mailboxes match 2529 the canonical LIST pattern. 2531 Let's assume there is the following hierarchy: 2533 C: D01 LIST "" "*" 2534 S: * LIST (\Marked \NoInferiors) "/" "inbox" 2535 S: * LIST () "/" "foo2" 2536 S: * LIST () "/" "foo2/bar1" 2537 S: * LIST () "/" "foo2/bar2" 2538 S: * LIST () "/" "baz2" 2539 S: * LIST () "/" "baz2/bar2" 2540 S: * LIST () "/" "baz2/bar22" 2541 S: * LIST () "/" "baz2/bar222" 2542 S: * LIST () "/" "eps2" 2543 S: * LIST () "/" "eps2/mamba" 2544 S: * LIST () "/" "qux2/bar2" 2545 S: D01 OK done 2547 And that the following mailboxes are subscribed: 2549 C: D02 LIST (SUBSCRIBED) "" "*" 2550 S: * LIST (\Subscribed) "/" "foo2/bar1" 2551 S: * LIST (\Subscribed) "/" "foo2/bar2" 2552 S: * LIST (\Subscribed) "/" "baz2/bar2" 2553 S: * LIST (\Subscribed) "/" "baz2/bar22" 2554 S: * LIST (\Subscribed) "/" "baz2/bar222" 2555 S: * LIST (\Subscribed) "/" "eps2" 2556 S: * LIST (\Subscribed) "/" "eps2/mamba" 2557 S: * LIST (\Subscribed) "/" "qux2/bar2" 2558 S: D02 OK done 2560 The client issues the following command first: 2562 C: D03 LIST (RECURSIVEMATCH SUBSCRIBED) "" "*2" 2563 S: * LIST () "/" "foo2" ("CHILDINFO" ("SUBSCRIBED")) 2564 S: * LIST (\Subscribed) "/" "foo2/bar2" 2565 S: * LIST (\Subscribed) "/" "baz2/bar2" 2566 S: * LIST (\Subscribed) "/" "baz2/bar22" 2567 S: * LIST (\Subscribed) "/" "baz2/bar222" 2568 S: * LIST (\Subscribed) "/" "eps2" ("CHILDINFO" ("SUBSCRIBED")) 2569 S: * LIST (\Subscribed) "/" "qux2/bar2" 2570 S: D03 OK done 2572 and the server may also include (but this would violate a SHOULD 2573 NOT in Section 3.5, because CHILDINFO is redundant) 2575 S: * LIST () "/" "baz2" ("CHILDINFO" ("SUBSCRIBED")) 2576 S: * LIST (\NonExistent) "/" "qux2" ("CHILDINFO" ("SUBSCRIBED")) 2578 The CHILDINFO extended data item is returned for mailboxes 2579 "foo2", "baz2", and "eps2", because all of them have subscribed 2580 children, even though for the mailbox "foo2" only one of the two 2581 subscribed children matches the pattern, for the mailbox "baz2" 2582 all the subscribed children match the pattern, and for the 2583 mailbox "eps2" none of the subscribed children matches the 2584 pattern. 2586 Note that if the client issues 2588 C: D03 LIST (RECURSIVEMATCH SUBSCRIBED) "" "*" 2589 S: * LIST () "/" "foo2" ("CHILDINFO" ("SUBSCRIBED")) 2590 S: * LIST (\Subscribed) "/" "foo2/bar1" 2591 S: * LIST (\Subscribed) "/" "foo2/bar2" 2592 S: * LIST () "/" "baz2" ("CHILDINFO" ("SUBSCRIBED")) 2593 S: * LIST (\Subscribed) "/" "baz2/bar2" 2594 S: * LIST (\Subscribed) "/" "baz2/bar22" 2595 S: * LIST (\Subscribed) "/" "baz2/bar222" 2596 S: * LIST (\Subscribed) "/" "eps2" ("CHILDINFO" ("SUBSCRIBED")) 2597 S: * LIST (\Subscribed) "/" "eps2/mamba" 2598 S: * LIST (\Subscribed) "/" "qux2/bar2" 2599 S: D03 OK done 2601 The LIST responses for mailboxes "foo2", "baz2", and "eps2" 2602 still have the CHILDINFO extended data item, even though this 2603 information is redundant and the client can determine it by 2604 itself. 2606 10: The following example shows usage of multiple mailbox patterns. 2607 It also demonstrates that the presence of the CHILDINFO extended 2608 data item doesn't necessarily imply \HasChildren. 2610 C: a1 LIST "" ("foo" "foo/*") 2611 S: * LIST () "/" foo 2612 S: a1 OK done 2614 C: a2 LIST (SUBSCRIBED) "" "foo/*" 2615 S: * LIST (\Subscribed \NonExistent) "/" foo/bar 2616 S: a2 OK done 2618 C: a3 LIST (SUBSCRIBED RECURSIVEMATCH) "" foo RETURN (CHILDREN) 2619 S: * LIST (\HasNoChildren) "/" foo ("CHILDINFO" ("SUBSCRIBED")) 2620 S: a3 OK done 2622 11: The following example shows how a server that supports missing 2623 mailbox hierarchy elements can signal to a client that didn't 2624 specify the RECURSIVEMATCH selection option that there is a 2625 child mailbox that matches the selection criteria. 2627 C: a1 LIST (REMOTE) "" * 2628 S: * LIST () "/" music/rock 2629 S: * LIST (\Remote) "/" also/jazz 2630 S: a1 OK done 2632 C: a2 LIST () "" % 2633 S: * LIST (\NonExistent \HasChildren) "/" music 2634 S: a2 OK done 2636 C: a3 LIST (REMOTE) "" % 2637 S: * LIST (\NonExistent \HasChildren) "/" music 2638 S: * LIST (\NonExistent \HasChildren) "/" also 2639 S: a3 OK done 2641 C: a3.1 LIST "" (% music/rock) 2642 S: * LIST () "/" music/rock 2643 S: a3.1 OK done 2645 Because "music/rock" is the only mailbox under "music", there's 2646 no need for the server to also return "music". However clients 2647 must handle both cases. 2649 6.3.10. LSUB Command 2651 Arguments: reference name 2652 mailbox name with possible wildcards 2654 Responses: untagged responses: LSUB 2656 Result: OK - lsub completed 2657 NO - lsub failure: can't list that reference or name 2658 BAD - command unknown or arguments invalid 2660 The LSUB command returns a subset of names from the set of names that 2661 the user has declared as being "active" or "subscribed". Zero or 2662 more untagged LSUB replies are returned. The arguments to LSUB are 2663 in the same form as those for LIST. 2665 The returned untagged LSUB response MAY contain different mailbox 2666 flags from a LIST untagged response. If this should happen, the 2667 flags in the untagged LIST are considered more authoritative. 2669 A special situation occurs when using LSUB with the % wildcard. 2670 Consider what happens if "foo/bar" (with a hierarchy delimiter of 2671 "/") is subscribed but "foo" is not. A "%" wildcard to LSUB must 2672 return foo, not foo/bar, in the LSUB response, and it MUST be flagged 2673 with the \Noselect attribute. 2675 The server MUST NOT unilaterally remove an existing mailbox name from 2676 the subscription list even if a mailbox by that name no longer 2677 exists. 2679 Example: C: A002 LSUB "#news." "comp.mail.*" 2680 S: * LSUB () "." #news.comp.mail.mime 2681 S: * LSUB () "." #news.comp.mail.misc 2682 S: A002 OK LSUB completed 2683 C: A003 LSUB "#news." "comp.%" 2684 S: * LSUB (\NoSelect) "." #news.comp.mail 2685 S: A003 OK LSUB completed 2687 6.3.11. NAMESPACE Command 2689 Arguments: none 2691 Responses: REQUIRED untagged responses: NAMESPACE 2693 Result: OK - command completed 2694 NO - Can't complete the command 2695 BAD - arguments invalid 2697 The NAMESPACE command causes a single ungagged NAMESPACE response to 2698 be returned. The untagged NAMESPACE response contains the prefix and 2699 hierarchy delimiter to the server's Personal Namespace(s), Other 2700 Users' Namespace(s), and Shared Namespace(s) that the server wishes 2701 to expose. The response will contain a NIL for any namespace class 2702 that is not available. Namespace-Response-Extensions ABNF non 2703 terminal is defined for extensibility and MAY be included in the 2704 response. Namespace-Response-Extensions which are not on the IETF 2705 standards track, MUST be prefixed with an "X-". 2707 Example 1: 2709 In this example a server supports a single personal namespace. No 2710 leading prefix is used on personal mailboxes and "/" is the hierarchy 2711 delimiter. 2713 C: A001 NAMESPACE 2714 S: * NAMESPACE (("" "/")) NIL NIL 2715 S: A001 OK NAMESPACE command completed 2717 Example 2: 2719 A user logged on anonymously to a server. No personal mailboxes are 2720 associated with the anonymous user and the user does not have access 2721 to the Other Users' Namespace. No prefix is required to access 2722 shared mailboxes and the hierarchy delimiter is "." 2723 C: A001 NAMESPACE 2724 S: * NAMESPACE NIL NIL (("" ".")) 2725 S: A001 OK NAMESPACE command completed 2727 Example 3: 2729 A server that contains a Personal Namespace and a single Shared 2730 Namespace. 2732 C: A001 NAMESPACE 2733 S: * NAMESPACE (("" "/")) NIL (("Public Folders/" "/")) 2734 S: A001 OK NAMESPACE command completed 2736 Example 4: 2738 A server that contains a Personal Namespace, Other Users' Namespace 2739 and multiple Shared Namespaces. Note that the hierarchy delimiter 2740 used within each namespace can be different. 2742 C: A001 NAMESPACE 2743 S: * NAMESPACE (("" "/")) (("~" "/")) (("#shared/" "/") 2744 ("#public/" "/")("#ftp/" "/")("#news." ".")) 2745 S: A001 OK NAMESPACE command completed 2747 The prefix string allows a client to do things such as automatically 2748 creating personal mailboxes or LISTing all available mailboxes within 2749 a namespace. 2751 Example 5: 2753 A server that supports only the Personal Namespace, with a leading 2754 prefix of INBOX to personal mailboxes and a hierarchy delimiter of 2755 "." 2757 C: A001 NAMESPACE 2758 S: * NAMESPACE (("INBOX." ".")) NIL NIL 2759 S: A001 OK NAMESPACE command completed 2761 < Automatically create a mailbox to store sent items.> 2763 C: A002 CREATE "INBOX.Sent Mail" 2764 S: A002 OK CREATE command completed 2766 Although typically a server will support only a single Personal 2767 Namespace, and a single Other User's Namespace, circumstances exist 2768 where there MAY be multiples of these, and a client MUST be prepared 2769 for them. If a client is configured such that it is required to 2770 create a certain mailbox, there can be circumstances where it is 2771 unclear which Personal Namespaces it should create the mailbox in. 2772 In these situations a client SHOULD let the user select which 2773 namespaces to create the mailbox in or just use the first personal 2774 namespace. 2776 Example 6: 2778 In this example, a server supports 2 Personal Namespaces. In 2779 addition to the regular Personal Namespace, the user has an 2780 additional personal namespace to allow access to mailboxes in an MH 2781 format mailstore. 2783 The client is configured to save a copy of all mail sent by the user 2784 into a mailbox called 'Sent Mail'. Furthermore, after a message is 2785 deleted from a mailbox, the client is configured to move that message 2786 to a mailbox called 'Deleted Items'. 2788 Note that this example demonstrates how some extension flags can be 2789 passed to further describe the #mh namespace. 2791 C: A001 NAMESPACE 2792 S: * NAMESPACE (("" "/")("#mh/" "/" "X-PARAM" ("FLAG1" "FLAG2"))) 2793 NIL NIL 2794 S: A001 OK NAMESPACE command completed 2796 < It is desired to keep only one copy of sent mail. It is unclear 2797 which Personal Namespace the client should use to create the 'Sent 2798 Mail' mailbox. The user is prompted to select a namespace and 2799 only one 'Sent Mail' mailbox is created. > 2801 C: A002 CREATE "Sent Mail" 2802 S: A002 OK CREATE command completed 2804 < The client is designed so that it keeps two 'Deleted Items' 2805 mailboxes, one for each namespace. > 2807 C: A003 CREATE "Delete Items" 2808 S: A003 OK CREATE command completed 2810 C: A004 CREATE "#mh/Deleted Items" 2811 S: A004 OK CREATE command completed 2813 The next level of hierarchy following the Other Users' Namespace 2814 prefix SHOULD consist of , where is a user name 2815 as per the LOGIN or AUTHENTICATE command. 2817 A client can construct a LIST command by appending a "%" to the Other 2818 Users' Namespace prefix to discover the Personal Namespaces of other 2819 users that are available to the currently authenticated user. 2821 In response to such a LIST command, a server SHOULD NOT return user 2822 names that have not granted access to their personal mailboxes to the 2823 user in question. 2825 A server MAY return a LIST response containing only the names of 2826 users that have explicitly granted access to the user in question. 2828 Alternatively, a server MAY return NO to such a LIST command, 2829 requiring that a user name be included with the Other Users' 2830 Namespace prefix before listing any other user's mailboxes. 2832 Example 7: 2834 A server that supports providing a list of other user's mailboxes 2835 that are accessible to the currently logged on user. 2837 C: A001 NAMESPACE 2838 S: * NAMESPACE (("" "/")) (("Other Users/" "/")) NIL 2839 S: A001 OK NAMESPACE command completed 2841 C: A002 LIST "" "Other Users/%" 2842 S: * LIST () "/" "Other Users/Mike" 2843 S: * LIST () "/" "Other Users/Karen" 2844 S: * LIST () "/" "Other Users/Matthew" 2845 S: * LIST () "/" "Other Users/Tesa" 2846 S: A002 OK LIST command completed 2848 Example 8: 2850 A server that does not support providing a list of other user's 2851 mailboxes that are accessible to the currently logged on user. The 2852 mailboxes are listable if the client includes the name of the other 2853 user with the Other Users' Namespace prefix. 2855 C: A001 NAMESPACE 2856 S: * NAMESPACE (("" "/")) (("#Users/" "/")) NIL 2857 S: A001 OK NAMESPACE command completed 2859 < In this example, the currently logged on user has access to the 2860 Personal Namespace of user Mike, but the server chose to suppress 2861 this information in the LIST response. However, by appending the 2862 user name Mike (received through user input) to the Other Users' 2863 Namespace prefix, the client is able to get a listing of the 2864 personal mailboxes of user Mike. > 2866 C: A002 LIST "" "#Users/%" 2867 S: A002 NO The requested item could not be found. 2869 C: A003 LIST "" "#Users/Mike/%" 2870 S: * LIST () "/" "#Users/Mike/INBOX" 2871 S: * LIST () "/" "#Users/Mike/Foo" 2872 S: A003 OK LIST command completed. 2874 A prefix string might not contain a hierarchy delimiter, because in 2875 some cases it is not needed as part of the prefix. 2877 Example 9: 2879 A server that allows access to the Other Users' Namespace by 2880 prefixing the others' mailboxes with a '~' followed by , 2881 where is a user name as per the LOGIN or AUTHENTICATE 2882 command. 2884 C: A001 NAMESPACE 2885 S: * NAMESPACE (("" "/")) (("~" "/")) NIL 2886 S: A001 OK NAMESPACE command completed 2888 < List the mailboxes for user mark > 2890 C: A002 LIST "" "~mark/%" 2891 S: * LIST () "/" "~mark/INBOX" 2892 S: * LIST () "/" "~mark/foo" 2893 S: A002 OK LIST command completed 2895 6.3.12. STATUS Command 2897 Arguments: mailbox name 2898 status data item names 2900 Responses: REQUIRED untagged responses: STATUS 2902 Result: OK - status completed 2903 NO - status failure: no status for that name 2904 BAD - command unknown or arguments invalid 2906 The STATUS command requests the status of the indicated mailbox. It 2907 does not change the currently selected mailbox, nor does it affect 2908 the state of any messages in the queried mailbox. 2910 The STATUS command provides an alternative to opening a second 2911 IMAP4rev2 connection and doing an EXAMINE command on a mailbox to 2912 query that mailbox's status without deselecting the current mailbox 2913 in the first IMAP4rev2 connection. 2915 Unlike the LIST command, the STATUS command is not guaranteed to be 2916 fast in its response. Under certain circumstances, it can be quite 2917 slow. In some implementations, the server is obliged to open the 2918 mailbox read-only internally to obtain certain status information. 2919 Also unlike the LIST command, the STATUS command does not accept 2920 wildcards. 2922 Note: The STATUS command is intended to access the status of 2923 mailboxes other than the currently selected mailbox. Because the 2924 STATUS command can cause the mailbox to be opened internally, and 2925 because this information is available by other means on the 2926 selected mailbox, the STATUS command SHOULD NOT be used on the 2927 currently selected mailbox. 2929 The STATUS command MUST NOT be used as a "check for new messages 2930 in the selected mailbox" operation (refer to sections Section 7, 2931 Section 7.3.1 for more information about the proper method for new 2932 message checking). 2934 Because the STATUS command is not guaranteed to be fast in its 2935 results, clients SHOULD NOT expect to be able to issue many 2936 consecutive STATUS commands and obtain reasonable performance. 2938 The currently defined status data items that can be requested are: 2940 MESSAGES The number of messages in the mailbox. 2942 UIDNEXT The next unique identifier value of the mailbox. Refer to 2943 Section 2.3.1.1 for more information. 2945 UIDVALIDITY The unique identifier validity value of the mailbox. 2946 Refer to Section 2.3.1.1 for more information. 2948 UNSEEN The number of messages which do not have the \Seen flag set. 2950 SIZE The total size of the mailbox in octets. This is not strictly 2951 required to be an exact value, but it MUST be equal to or greater 2952 than the sum of the values of the RFC822.SIZE FETCH message data 2953 items (see Section 6.4.5) of all messages in the mailbox. 2955 Example: C: A042 STATUS blurdybloop (UIDNEXT MESSAGES) 2956 S: * STATUS blurdybloop (MESSAGES 231 UIDNEXT 44292) 2957 S: A042 OK STATUS completed 2959 6.3.13. APPEND Command 2961 Arguments: mailbox name 2962 OPTIONAL flag parenthesized list 2963 OPTIONAL date/time string 2964 message literal 2966 Responses: no specific responses for this command 2968 Result: OK - append completed 2969 NO - append error: can't append to that mailbox, error 2970 in flags or date/time or message text 2971 BAD - command unknown or arguments invalid 2973 The APPEND command appends the literal argument as a new message to 2974 the end of the specified destination mailbox. This argument SHOULD 2975 be in the format of an [RFC-5322] or [I18N-HDRS] message. 8-bit 2976 characters are permitted in the message. A server implementation 2977 that is unable to preserve 8-bit data properly MUST be able to 2978 reversibly convert 8-bit APPEND data to 7-bit using a [MIME-IMB] 2979 content transfer encoding. 2981 Note: There may be exceptions, e.g., draft messages, in which 2982 required [RFC-5322] header lines are omitted in the message 2983 literal argument to APPEND. The full implications of doing so 2984 must be understood and carefully weighed. 2986 If a flag parenthesized list is specified, the flags SHOULD be set in 2987 the resulting message; otherwise, the flag list of the resulting 2988 message is set to empty by default. 2990 If a date-time is specified, the internal date SHOULD be set in the 2991 resulting message; otherwise, the internal date of the resulting 2992 message is set to the current date and time by default. 2994 If the append is unsuccessful for any reason, the mailbox MUST be 2995 restored to its state before the APPEND attempt; no partial appending 2996 is permitted. 2998 If the destination mailbox does not exist, a server MUST return an 2999 error, and MUST NOT automatically create the mailbox. Unless it is 3000 certain that the destination mailbox can not be created, the server 3001 MUST send the response code "[TRYCREATE]" as the prefix of the text 3002 of the tagged NO response. This gives a hint to the client that it 3003 can attempt a CREATE command and retry the APPEND if the CREATE is 3004 successful. 3006 On successful completion of an APPEND, the server SHOULD return an 3007 APPENDUID response code. 3009 In the case of a mailbox that has permissions set so that the client 3010 can APPEND to the mailbox, but not SELECT or EXAMINE it, the server 3011 SHOULD NOT send an APPENDUID response code as it would disclose 3012 information about the mailbox. 3014 In the case of a mailbox that has UIDNOTSTICKY status (see 3015 UIDNOTSTICKY response code definition), the server MAY omit the 3016 APPENDUID response code as it is not meaningful. 3018 If the server does not return the APPENDUID response codes, the 3019 client can discover this information by selecting the destination 3020 mailbox. The location of messages placed in the destination mailbox 3021 by APPEND can be determined by using FETCH and/or SEARCH commands 3022 (e.g., for Message-ID or some unique marker placed in the message in 3023 an APPEND). 3025 If the mailbox is currently selected, the normal new message actions 3026 SHOULD occur. Specifically, the server SHOULD notify the client 3027 immediately via an untagged EXISTS response. If the server does not 3028 do so, the client MAY issue a NOOP command after one or more APPEND 3029 commands. 3031 Example: C: A003 APPEND saved-messages (\Seen) {310} 3032 S: + Ready for literal data 3033 C: Date: Mon, 7 Feb 1994 21:52:25 -0800 (PST) 3034 C: From: Fred Foobar 3035 C: Subject: afternoon meeting 3036 C: To: mooch@owatagu.siam.edu 3037 C: Message-Id: 3038 C: MIME-Version: 1.0 3039 C: Content-Type: TEXT/PLAIN; CHARSET=US-ASCII 3040 C: 3041 C: Hello Joe, do you think we can meet at 3:30 tomorrow? 3042 C: 3043 S: A003 OK APPEND completed 3045 Example: C: A003 APPEND saved-messages (\Seen) {297} 3046 C: Date: Mon, 7 Feb 1994 21:52:25 -0800 (PST) 3047 C: From: Fred Foobar 3048 C: Subject: afternoon meeting 3049 C: To: mooch@example.com 3050 C: Message-Id: 3051 C: MIME-Version: 1.0 3052 C: Content-Type: TEXT/PLAIN; CHARSET=US-ASCII 3053 C: 3054 C: Hello Joe, do you think we can meet at 3:30 tomorrow? 3055 C: 3056 S: A003 OK [APPENDUID 38505 3955] APPEND completed 3057 C: A004 COPY 2:4 meeting 3058 S: A004 OK [COPYUID 38505 304,319:320 3956:3958] Done 3059 C: A005 UID COPY 305:310 meeting 3060 S: A005 OK No matching messages, so nothing copied 3061 C: A006 COPY 2 funny 3062 S: A006 OK Done 3063 C: A007 SELECT funny 3064 S: * 1 EXISTS 3065 S: * OK [UIDVALIDITY 3857529045] Validity session-only 3066 S: * OK [UIDNEXT 2] Predicted next UID 3067 S: * NO [UIDNOTSTICKY] Non-persistent UIDs 3068 S: * FLAGS (\Answered \Flagged \Deleted \Seen \Draft) 3069 S: * OK [PERMANENTFLAGS (\Deleted \Seen)] Limited 3070 S: A007 OK [READ-WRITE] SELECT completed 3072 In this example, A003 and A004 demonstrate successful appending and 3073 copying to a mailbox that returns the UIDs assigned to the messages. 3074 A005 is an example in which no messages were copied; this is because 3075 in A003, we see that message 2 had UID 304, and message 3 had UID 3076 319; therefore, UIDs 305 through 310 do not exist (refer to 3077 Section 2.3.1.1 for further explanation). A006 is an example of a 3078 message being copied that did not return a COPYUID; and, as expected, 3079 A007 shows that the mail store containing that mailbox does not 3080 support persistent UIDs. 3082 Note: The APPEND command is not used for message delivery, because 3083 it does not provide a mechanism to transfer [SMTP] envelope 3084 information. 3086 6.3.14. IDLE Command 3088 Arguments: none 3090 Responses: continuation data will be requested; the client sends the 3091 continuation data "DONE" to end the command 3093 Result: OK - IDLE completed after client sent "DONE" 3094 NO - failure: the server will not allow the IDLE command 3095 at this time 3096 BAD - command unknown or arguments invalid 3098 Without the IDLE command a client requires to poll the server for 3099 changes to the selected mailbox (new mail, deletions, flag changes). 3100 It's often more desirable to have the server transmit updates to the 3101 client in real time. This allows a user to see new mail immediately. 3102 The IDLE command allows a client to tell the server that it's ready 3103 to accept such real-time updates. 3105 The IDLE command is sent from the client to the server when the 3106 client is ready to accept unsolicited mailbox update messages. The 3107 server requests a response to the IDLE command using the continuation 3108 ("+") response. The IDLE command remains active until the client 3109 responds to the continuation, and as long as an IDLE command is 3110 active, the server is now free to send untagged EXISTS, EXPUNGE, 3111 FETCH, and other responses at any time. If the server choose to send 3112 unsolicited FETCH responses, they MUST include UID FETCH item. 3114 The IDLE command is terminated by the receipt of a "DONE" 3115 continuation from the client; such response satisfies the server's 3116 continuation request. At that point, the server MAY send any 3117 remaining queued untagged responses and then MUST immediately send 3118 the tagged response to the IDLE command and prepare to process other 3119 commands. As for other commands, the processing of any new command 3120 may cause the sending of unsolicited untagged responses, subject to 3121 the ambiguity limitations. The client MUST NOT send a command while 3122 the server is waiting for the DONE, since the server will not be able 3123 to distinguish a command from a continuation. 3125 The server MAY consider a client inactive if it has an IDLE command 3126 running, and if such a server has an inactivity timeout it MAY log 3127 the client off implicitly at the end of its timeout period. Because 3128 of that, clients using IDLE are advised to terminate the IDLE and re- 3129 issue it at least every 29 minutes to avoid being logged off. This 3130 still allows a client to receive immediate mailbox updates even 3131 though it need only "poll" at half hour intervals. 3133 Example: C: A001 SELECT INBOX 3134 S: * FLAGS (\Deleted \Seen \Flagged) 3135 S: * OK [PERMANENTFLAGS (\Deleted \Seen \Flagged)] Limited 3136 S: * 3 EXISTS 3137 S: * OK [UIDVALIDITY 1] 3138 S: A001 OK [READ-WRITE] SELECT completed 3139 C: A002 IDLE 3140 S: + idling 3141 ...time passes; new mail arrives... 3142 S: * 4 EXISTS 3143 C: DONE 3144 S: A002 OK IDLE terminated 3145 ...another client expunges message 2 now... 3146 C: A003 FETCH 4 ALL 3147 S: * 4 FETCH (...) 3148 S: A003 OK FETCH completed 3149 C: A004 IDLE 3150 S: * 2 EXPUNGE 3151 S: * 3 EXISTS 3152 S: + idling 3153 ...time passes; another client expunges message 3... 3154 S: * 3 EXPUNGE 3155 S: * 2 EXISTS 3156 ...time passes; new mail arrives... 3157 S: * 3 EXISTS 3158 C: DONE 3159 S: A004 OK IDLE terminated 3160 C: A005 FETCH 3 ALL 3161 S: * 3 FETCH (...) 3162 S: A005 OK FETCH completed 3163 C: A006 IDLE 3165 6.4. Client Commands - Selected State 3167 In the selected state, commands that manipulate messages in a mailbox 3168 are permitted. 3170 In addition to the universal commands (CAPABILITY, NOOP, and LOGOUT), 3171 and the authenticated state commands (SELECT, EXAMINE, NAMESPACE, 3172 CREATE, DELETE, RENAME, SUBSCRIBE, UNSUBSCRIBE, LIST, LSUB , STATUS, 3173 and APPEND), the following commands are valid in the selected state: 3174 CLOSE, UNSELECT, EXPUNGE, SEARCH, FETCH, STORE, COPY, MOVE, and UID. 3176 6.4.1. CLOSE Command 3178 Arguments: none 3180 Responses: no specific responses for this command 3181 Result: OK - close completed, now in authenticated state 3182 BAD - command unknown or arguments invalid 3184 The CLOSE command permanently removes all messages that have the 3185 \Deleted flag set from the currently selected mailbox, and returns to 3186 the authenticated state from the selected state. No untagged EXPUNGE 3187 responses are sent. 3189 No messages are removed, and no error is given, if the mailbox is 3190 selected by an EXAMINE command or is otherwise selected read-only. 3192 Even if a mailbox is selected, a SELECT, EXAMINE, or LOGOUT command 3193 MAY be issued without previously issuing a CLOSE command. The 3194 SELECT, EXAMINE, and LOGOUT commands implicitly close the currently 3195 selected mailbox without doing an expunge. However, when many 3196 messages are deleted, a CLOSE-LOGOUT or CLOSE-SELECT sequence is 3197 considerably faster than an EXPUNGE-LOGOUT or EXPUNGE-SELECT because 3198 no untagged EXPUNGE responses (which the client would probably 3199 ignore) are sent. 3201 Example: C: A341 CLOSE 3202 S: A341 OK CLOSE completed 3204 6.4.2. UNSELECT Command 3206 Arguments: none 3208 Responses: no specific responses for this command 3210 Result: OK - unselect completed, now in authenticated state 3211 BAD - no mailbox selected, or argument supplied but none 3212 permitted 3214 The UNSELECT command frees server's resources associated with the 3215 selected mailbox and returns the server to the authenticated state. 3216 This command performs the same actions as CLOSE, except that no 3217 messages are permanently removed from the currently selected mailbox. 3219 Example: C: A342 UNSELECT 3220 S: A342 OK Unselect completed 3222 6.4.3. EXPUNGE Command 3224 Arguments: none 3226 Responses: untagged responses: EXPUNGE 3228 Result: OK - expunge completed 3229 NO - expunge failure: can't expunge (e.g., permission 3230 denied) 3231 BAD - command unknown or arguments invalid 3233 The EXPUNGE command permanently removes all messages that have the 3234 \Deleted flag set from the currently selected mailbox. Before 3235 returning an OK to the client, an untagged EXPUNGE response is sent 3236 for each message that is removed. 3238 Example: C: A202 EXPUNGE 3239 S: * 3 EXPUNGE 3240 S: * 3 EXPUNGE 3241 S: * 5 EXPUNGE 3242 S: * 8 EXPUNGE 3243 S: A202 OK EXPUNGE completed 3245 Note: In this example, messages 3, 4, 7, and 11 had the \Deleted flag 3246 set. See the description of the EXPUNGE response for further 3247 explanation. 3249 6.4.4. SEARCH Command 3251 Arguments: OPTIONAL result specifier 3252 OPTIONAL [CHARSET] specification 3253 searching criteria (one or more) 3255 Responses: REQUIRED untagged response: ESEARCH 3257 Result: OK - search completed 3258 NO - search error: can't search that [CHARSET] or 3259 criteria 3260 BAD - command unknown or arguments invalid 3262 The SEARCH command searches the mailbox for messages that match the 3263 given searching criteria. 3265 The SEARCH command may contain result options. Result options 3266 control what kind of information is returned about messages matching 3267 the search criteria in an untagged ESEARCH response. If no result 3268 option is specified or empty list of options is specified "()", ALL 3269 is assumed (see below). The order of individual options is 3270 arbitrary. Individual options may contain parameters enclosed in 3271 parentheses (*). If an option has parameters, they consist of atoms 3272 and/or strings and/or lists in a specific order. Any options not 3273 defined by extensions that the server supports must be rejected with 3274 a BAD response. 3276 (*) - if an option has a mandatory parameter, which can always be 3277 represented as a number or a sequence-set, the option parameter does 3278 not need the enclosing (). See ABNF for more details. 3280 This document specifies the following result options: 3282 MIN 3284 Return the lowest message number/UID that satisfies the SEARCH 3285 criteria. 3287 If the SEARCH results in no matches, the server MUST NOT 3288 include the MIN result option in the ESEARCH response; however, 3289 it still MUST send the ESEARCH response. 3291 MAX 3293 Return the highest message number/UID that satisfies the SEARCH 3294 criteria. 3296 If the SEARCH results in no matches, the server MUST NOT 3297 include the MAX result option in the ESEARCH response; however, 3298 it still MUST send the ESEARCH response. 3300 ALL 3302 Return all message numbers/UIDs that satisfy the SEARCH 3303 criteria using the sequence-set syntax. Note, the client MUST 3304 NOT assume that messages/UIDs will be listed in any particular 3305 order. 3307 If the SEARCH results in no matches, the server MUST NOT 3308 include the ALL result option in the ESEARCH response; however, 3309 it still MUST send the ESEARCH response. 3311 COUNT Return number of the messages that satisfy the SEARCH 3312 criteria. This result option MUST always be included in the 3313 ESEARCH response. 3315 Note: future extensions to this document can allow servers to return 3316 multiple ESEARCH responses for a single extended SEARCH command. 3317 However all options specified above MUST result in a single ESEARCH 3318 response. These extensions will have to describe how results from 3319 multiple ESEARCH responses are to be amalgamated. 3321 Searching criteria consist of one or more search keys. 3323 When multiple keys are specified, the result is the intersection (AND 3324 function) of all the messages that match those keys. For example, 3325 the criteria DELETED FROM "SMITH" SINCE 1-Feb-1994 refers to all 3326 deleted messages from Smith that were placed in the mailbox since 3327 February 1, 1994. A search key can also be a parenthesized list of 3328 one or more search keys (e.g., for use with the OR and NOT keys). 3330 Server implementations MAY exclude [MIME-IMB] body parts with 3331 terminal content media types other than TEXT and MESSAGE from 3332 consideration in SEARCH matching. 3334 The OPTIONAL [CHARSET] specification consists of the word "CHARSET" 3335 followed by a registered [CHARSET]. It indicates the [CHARSET] of 3336 the strings that appear in the search criteria. [MIME-IMB] content 3337 transfer encodings, and [MIME-HDRS] strings in [RFC-5322]/[MIME-IMB] 3338 headers, MUST be decoded before comparing text. US-ASCII and UTF-8 3339 charsets MUST be supported; other [CHARSET]s MAY be supported. If 3340 "CHARSET" is not provided, an IMAP4rev2 server MUST assume UTF-8. 3342 If the server does not support the specified [CHARSET], it MUST 3343 return a tagged NO response (not a BAD). This response SHOULD 3344 contain the BADCHARSET response code, which MAY list the [CHARSET]s 3345 supported by the server. 3347 In all search keys that use strings, a message matches the key if the 3348 string is a substring of the associated text. The matching SHOULD be 3349 case-insensitive for characters within ASCII range. Consider using 3350 [IMAP-I18N] for language-sensitive case-insensitive searching. Note 3351 that the empty string is a substring; this is useful when doing a 3352 HEADER search in order to test for a header field presence in the 3353 message. 3355 The defined search keys are as follows. Refer to the Formal Syntax 3356 section for the precise syntactic definitions of the arguments. 3358 Messages with message sequence numbers corresponding 3359 to the specified message sequence number set. 3361 ALL All messages in the mailbox; the default initial key for ANDing. 3363 ANSWERED Messages with the \Answered flag set. 3365 BCC Messages that contain the specified string in the 3366 envelope structure's BCC field. 3368 BEFORE Messages whose internal date (disregarding time and 3369 timezone) is earlier than the specified date. 3371 BODY Messages that contain the specified string in the body 3372 of the message. Unlike TEXT (see below), this doesn't match any 3373 header fields. 3375 CC Messages that contain the specified string in the 3376 envelope structure's CC field. 3378 DELETED Messages with the \Deleted flag set. 3380 DRAFT Messages with the \Draft flag set. 3382 FLAGGED Messages with the \Flagged flag set. 3384 FROM Messages that contain the specified string in the 3385 envelope structure's FROM field. 3387 HEADER Messages that have a header with the 3388 specified field-name (as defined in [RFC-5322]) and that contains 3389 the specified string in the text of the header (what comes after 3390 the colon). If the string to search is zero-length, this matches 3391 all messages that have a header line with the specified field-name 3392 regardless of the contents. 3394 KEYWORD Messages with the specified keyword flag set. 3396 LARGER Messages with an [RFC-5322] size larger than the 3397 specified number of octets. 3399 NEW [[Fix this]] Messages that have the \Recent flag set but not the 3400 \Seen flag. This is functionally equivalent to "(RECENT UNSEEN)". 3402 NOT Messages that do not match the specified search 3403 key. 3405 ON Messages whose internal date (disregarding time and 3406 timezone) is within the specified date. 3408 OR Messages that match either search 3409 key. 3411 SEEN Messages that have the \Seen flag set. 3413 SENTBEFORE Messages whose [RFC-5322] Date: header 3414 (disregarding time and timezone) is earlier than the specified 3415 date. 3417 SENTON Messages whose [RFC-5322] Date: header (disregarding 3418 time and timezone) is within the specified date. 3420 SENTSINCE Messages whose [RFC-5322] Date: header 3421 (disregarding time and timezone) is within or later than the 3422 specified date. 3424 SINCE Messages whose internal date (disregarding time and 3425 timezone) is within or later than the specified date. 3427 SMALLER Messages with an [RFC-5322] size smaller than the 3428 specified number of octets. 3430 SUBJECT Messages that contain the specified string in the 3431 envelope structure's SUBJECT field. 3433 TEXT Messages that contain the specified string in the 3434 header (including MIME header fields) or body of the message. 3436 TO Messages that contain the specified string in the 3437 envelope structure's TO field. 3439 UID Messages with unique identifiers corresponding to 3440 the specified unique identifier set. Sequence set ranges are 3441 permitted. 3443 UNANSWERED Messages that do not have the \Answered flag set. 3445 UNDELETED Messages that do not have the \Deleted flag set. 3447 UNDRAFT Messages that do not have the \Draft flag set. 3449 UNFLAGGED Messages that do not have the \Flagged flag set. 3451 UNKEYWORD Messages that do not have the specified keyword 3452 flag set. 3454 UNSEEN Messages that do not have the \Seen flag set. 3456 Example: C: A282 SEARCH RETURN (MIN COUNT) FLAGGED 3457 SINCE 1-Feb-1994 NOT FROM "Smith" 3458 S: * ESEARCH (TAG "A282") MIN 2 COUNT 3 3459 S: A282 OK SEARCH completed 3461 Example: C: A283 SEARCH RETURN () FLAGGED 3462 SINCE 1-Feb-1994 NOT FROM "Smith" 3463 S: * ESEARCH (TAG "A283") ALL 2,10:11 3464 S: A283 OK SEARCH completed 3466 Example: C: A284 SEARCH TEXT "string not in mailbox" 3467 S: * ESEARCH (TAG "A284") 3468 S: A284 OK SEARCH completed 3469 C: A285 SEARCH CHARSET UTF-8 TEXT {6} 3470 S: + Ready for literal text 3471 C: XXXXXX 3472 S: * ESEARCH (TAG "A285") ALL 43 3473 S: A285 OK SEARCH completed 3475 Note: Since this document is restricted to 7-bit ASCII text, it is 3476 not possible to show actual UTF-8 data. The "XXXXXX" is a 3477 placeholder for what would be 6 octets of 8-bit data in an actual 3478 transaction. 3480 The following example demonstrates finding the first unseen message 3481 in the mailbox: 3483 Example: C: A284 SEARCH RETURN (MIN) UNSEEN 3484 S: * ESEARCH (TAG "A284") MIN 4 3485 S: A284 OK SEARCH completed 3487 The following example demonstrates that if the ESEARCH UID indicator 3488 is present, all data in the ESEARCH response is referring to UIDs; 3489 for example, the MIN result specifier will be followed by a UID. 3491 Example: C: A285 UID SEARCH RETURN (MIN MAX) 1:5000 3492 S: * ESEARCH (TAG "A285") UID MIN 7 MAX 3800 3493 S: A285 OK SEARCH completed 3495 The following example demonstrates returning the number of deleted 3496 messages: 3498 Example: C: A286 SEARCH RETURN (COUNT) DELETED 3499 S: * ESEARCH (TAG "A286") COUNT 15 3500 S: A286 OK SEARCH completed 3502 6.4.5. FETCH Command 3504 Arguments: sequence set 3505 message data item names or macro 3507 Responses: untagged responses: FETCH 3509 Result: OK - fetch completed 3510 NO - fetch error: can't fetch that data 3511 BAD - command unknown or arguments invalid 3513 The FETCH command retrieves data associated with a message in the 3514 mailbox. The data items to be fetched can be either a single atom or 3515 a parenthesized list. 3517 Most data items, identified in the formal syntax under the msg-att- 3518 static rule, are static and MUST NOT change for any particular 3519 message. Other data items, identified in the formal syntax under the 3520 msg-att-dynamic rule, MAY change, either as a result of a STORE 3521 command or due to external events. 3523 For example, if a client receives an ENVELOPE for a message when 3524 it already knows the envelope, it can safely ignore the newly 3525 transmitted envelope. 3527 There are three macros which specify commonly-used sets of data 3528 items, and can be used instead of data items. A macro must be used 3529 by itself, and not in conjunction with other macros or data items. 3531 ALL Macro equivalent to: (FLAGS INTERNALDATE RFC822.SIZE ENVELOPE) 3533 FAST Macro equivalent to: (FLAGS INTERNALDATE RFC822.SIZE) 3535 FULL Macro equivalent to: (FLAGS INTERNALDATE RFC822.SIZE ENVELOPE 3536 BODY) 3538 The currently defined data items that can be fetched are: 3540 BINARY[]<> 3542 Requests that the specified section be transmitted after 3543 performing Content-Transfer-Encoding-related decoding. 3545 The argument, if present, requests that a subset of 3546 the data be returned. The semantics of a partial FETCH BINARY 3547 command are the same as for a partial FETCH BODY command, with 3548 the exception that the arguments refer to the DECODED 3549 section data. 3551 BINARY.PEEK[]<> An alternate form of 3552 BINARY[] that does not implicitly set the \Seen 3553 flag. 3555 BINARY.SIZE[] 3557 Requests the decoded size of the section (i.e., the size to 3558 expect in response to the corresponding FETCH BINARY request). 3560 Note: client authors are cautioned that this might be an 3561 expensive operation for some server implementations. 3562 Needlessly issuing this request could result in degraded 3563 performance due to servers having to calculate the value every 3564 time the request is issued. 3566 BODY Non-extensible form of BODYSTRUCTURE. 3568 BODY[
]<> 3570 The text of a particular body section. The section 3571 specification is a set of zero or more part specifiers 3572 delimited by periods. A part specifier is either a part number 3573 or one of the following: HEADER, HEADER.FIELDS, 3574 HEADER.FIELDS.NOT, MIME, and TEXT. An empty section 3575 specification refers to the entire message, including the 3576 header. 3578 Every message has at least one part number. Non-[MIME-IMB] 3579 messages, and non-multipart [MIME-IMB] messages with no 3580 encapsulated message, only have a part 1. 3582 Multipart messages are assigned consecutive part numbers, as 3583 they occur in the message. If a particular part is of type 3584 message or multipart, its parts MUST be indicated by a period 3585 followed by the part number within that nested multipart part. 3587 A part of type MESSAGE/RFC822 or MESSAGE/GLOBAL also has nested 3588 part numbers, referring to parts of the MESSAGE part's body. 3590 The HEADER, HEADER.FIELDS, HEADER.FIELDS.NOT, and TEXT part 3591 specifiers can be the sole part specifier or can be prefixed by 3592 one or more numeric part specifiers, provided that the numeric 3593 part specifier refers to a part of type MESSAGE/RFC822 or 3594 MESSAGE/GLOBAL. The MIME part specifier MUST be prefixed by 3595 one or more numeric part specifiers. 3597 The HEADER, HEADER.FIELDS, and HEADER.FIELDS.NOT part 3598 specifiers refer to the [RFC-5322] header of the message or of 3599 an encapsulated [MIME-IMT] MESSAGE/RFC822 or MESSAGE/GLOBAL 3600 message. HEADER.FIELDS and HEADER.FIELDS.NOT are followed by a 3601 list of field-name (as defined in [RFC-5322]) names, and return 3602 a subset of the header. The subset returned by HEADER.FIELDS 3603 contains only those header fields with a field-name that 3604 matches one of the names in the list; similarly, the subset 3605 returned by HEADER.FIELDS.NOT contains only the header fields 3606 with a non-matching field-name. The field-matching is ASCII 3607 range case-insensitive but otherwise exact. Subsetting does 3608 not exclude the [RFC-5322] delimiting blank line between the 3609 header and the body; the blank line is included in all header 3610 fetches, except in the case of a message which has no body and 3611 no blank line. 3613 The MIME part specifier refers to the [MIME-IMB] header for 3614 this part. 3616 The TEXT part specifier refers to the text body of the message, 3617 omitting the [RFC-5322] header. 3619 Here is an example of a complex message with some of its 3620 part specifiers: 3622 HEADER ([RFC-5322] header of the message) 3623 TEXT ([RFC-5322] text body of the message) MULTIPART/MIXED 3624 1 TEXT/PLAIN 3625 2 APPLICATION/OCTET-STREAM 3626 3 MESSAGE/RFC822 3627 3.HEADER ([RFC-5322] header of the message) 3628 3.TEXT ([RFC-5322] text body of the message) MULTIPART/MIXED 3629 3.1 TEXT/PLAIN 3630 3.2 APPLICATION/OCTET-STREAM 3631 4 MULTIPART/MIXED 3632 4.1 IMAGE/GIF 3633 4.1.MIME ([MIME-IMB] header for the IMAGE/GIF) 3634 4.2 MESSAGE/RFC822 3635 4.2.HEADER ([RFC-5322] header of the message) 3636 4.2.TEXT ([RFC-5322] text body of the message) MULTIPART/MIXED 3637 4.2.1 TEXT/PLAIN 3638 4.2.2 MULTIPART/ALTERNATIVE 3639 4.2.2.1 TEXT/PLAIN 3640 4.2.2.2 TEXT/RICHTEXT 3642 It is possible to fetch a substring of the designated text. 3643 This is done by appending an open angle bracket ("<"), the 3644 octet position of the first desired octet, a period, the 3645 maximum number of octets desired, and a close angle bracket 3646 (">") to the part specifier. If the starting octet is beyond 3647 the end of the text, an empty string is returned. 3649 Any partial fetch that attempts to read beyond the end of the 3650 text is truncated as appropriate. A partial fetch that starts 3651 at octet 0 is returned as a partial fetch, even if this 3652 truncation happened. 3654 Note: This means that BODY[]<0.2048> of a 1500-octet message 3655 will return BODY[]<0> with a literal of size 1500, not 3656 BODY[]. 3658 Note: A substring fetch of a HEADER.FIELDS or 3659 HEADER.FIELDS.NOT part specifier is calculated after 3660 subsetting the header. 3662 The \Seen flag is implicitly set; if this causes the flags to 3663 change, they SHOULD be included as part of the FETCH responses. 3665 BODY.PEEK[
]<> An alternate form of BODY[
] 3666 that does not implicitly set the \Seen flag. 3668 BODYSTRUCTURE The [MIME-IMB] body structure of the message. This is 3669 computed by the server by parsing the [MIME-IMB] header fields in 3670 the [RFC-5322] header and [MIME-IMB] headers. 3672 ENVELOPE The envelope structure of the message. This is computed by 3673 the server by parsing the [RFC-5322] header into the component 3674 parts, defaulting various fields as necessary. 3676 FLAGS The flags that are set for this message. 3678 INTERNALDATE The internal date of the message. 3680 RFC822 Functionally equivalent to BODY[], differing in the syntax of 3681 the resulting untagged FETCH data (RFC822 is returned). 3683 RFC822.HEADER Functionally equivalent to BODY.PEEK[HEADER], 3684 differing in the syntax of the resulting untagged FETCH data 3685 (RFC822.HEADER is returned). 3687 RFC822.SIZE The [RFC-5322] size of the message. 3689 RFC822.TEXT Functionally equivalent to BODY[TEXT], differing in the 3690 syntax of the resulting untagged FETCH data (RFC822.TEXT is 3691 returned). 3693 UID The unique identifier for the message. 3695 Example: C: A654 FETCH 2:4 (FLAGS BODY[HEADER.FIELDS (DATE FROM)]) 3696 S: * 2 FETCH .... 3697 S: * 3 FETCH .... 3698 S: * 4 FETCH .... 3699 S: A654 OK FETCH completed 3701 6.4.6. STORE Command 3703 Arguments: sequence set 3704 message data item name 3705 value for message data item 3707 Responses: untagged responses: FETCH 3709 Result: OK - store completed 3710 NO - store error: can't store that data 3711 BAD - command unknown or arguments invalid 3713 The STORE command alters data associated with a message in the 3714 mailbox. Normally, STORE will return the updated value of the data 3715 with an untagged FETCH response. A suffix of ".SILENT" in the data 3716 item name prevents the untagged FETCH, and the server SHOULD assume 3717 that the client has determined the updated value itself or does not 3718 care about the updated value. 3720 Note: Regardless of whether or not the ".SILENT" suffix was used, 3721 the server SHOULD send an untagged FETCH response if a change to a 3722 message's flags from an external source is observed. The intent 3723 is that the status of the flags is determinate without a race 3724 condition. 3726 The currently defined data items that can be stored are: 3728 FLAGS Replace the flags for the message with the 3729 argument. The new value of the flags is returned as if a FETCH of 3730 those flags was done. 3732 FLAGS.SILENT Equivalent to FLAGS, but without returning 3733 a new value. 3735 +FLAGS Add the argument to the flags for the message. 3736 The new value of the flags is returned as if a FETCH of those 3737 flags was done. 3739 +FLAGS.SILENT Equivalent to +FLAGS, but without 3740 returning a new value. 3742 -FLAGS Remove the argument from the flags for the 3743 message. The new value of the flags is returned as if a FETCH of 3744 those flags was done. 3746 -FLAGS.SILENT Equivalent to -FLAGS, but without 3747 returning a new value. 3749 Example: C: A003 STORE 2:4 +FLAGS (\Deleted) 3750 S: * 2 FETCH (FLAGS (\Deleted \Seen)) 3751 S: * 3 FETCH (FLAGS (\Deleted)) 3752 S: * 4 FETCH (FLAGS (\Deleted \Flagged \Seen)) 3753 S: A003 OK STORE completed 3755 6.4.7. COPY Command 3757 Arguments: sequence set 3758 mailbox name 3760 Responses: no specific responses for this command 3762 Result: OK - copy completed 3763 NO - copy error: can't copy those messages or to that 3764 name 3765 BAD - command unknown or arguments invalid 3767 The COPY command copies the specified message(s) to the end of the 3768 specified destination mailbox. The flags and internal date of the 3769 message(s) SHOULD be preserved in the copy. 3771 If the destination mailbox does not exist, a server SHOULD return an 3772 error. It SHOULD NOT automatically create the mailbox. Unless it is 3773 certain that the destination mailbox can not be created, the server 3774 MUST send the response code "[TRYCREATE]" as the prefix of the text 3775 of the tagged NO response. This gives a hint to the client that it 3776 can attempt a CREATE command and retry the COPY if the CREATE is 3777 successful. 3779 If the COPY command is unsuccessful for any reason, server 3780 implementations MUST restore the destination mailbox to its state 3781 before the COPY attempt. 3783 On successful completion of a COPY, the server SHOULD return a 3784 COPYUID response code. 3786 In the case of a mailbox that has permissions set so that the client 3787 can COPY to the mailbox, but not SELECT or EXAMINE it, the server 3788 SHOULD NOT send an COPYUID response code as it would disclose 3789 information about the mailbox. 3791 In the case of a mailbox that has UIDNOTSTICKY status (see the 3792 UIDNOTSTICKY response code), the server MAY omit the COPYUID response 3793 code as it is not meaningful. 3795 If the server does not return the COPYUID response code, the client 3796 can discover this information by selecting the destination mailbox. 3797 The location of messages placed in the destination mailbox by COPY 3798 can be determined by using FETCH and/or SEARCH commands (e.g., for 3799 Message-ID). 3801 Example: C: A003 COPY 2:4 MEETING 3802 S: A003 OK COPY completed 3804 6.4.8. MOVE Command 3806 Arguments: sequence set 3807 mailbox name 3809 Responses: no specific responses for this command 3811 Result: OK - move completed 3812 NO - move error: can't move those messages or to that 3813 name 3814 BAD - command unknown or arguments invalid 3816 The MOVE command moves the specified message(s) to the end of the 3817 specified destination mailbox. The flags and internal date of the 3818 message(s) SHOULD be preserved. 3820 This means that a new message is created in the target mailbox with a 3821 new UID, the original message is removed from the source mailbox, and 3822 it appears to the client as a single action. This has the same 3823 effect for each message as this sequence: 3825 1. [UID] COPY 3827 2. [UID] STORE +FLAGS.SILENT \DELETED 3829 3. UID EXPUNGE 3831 Although the effect of the MOVE is the same as the preceding steps, 3832 the semantics are not identical: The intermediate states produced by 3833 those steps do not occur, and the response codes are different. In 3834 particular, though the COPY and EXPUNGE response codes will be 3835 returned, response codes for a STORE MUST NOT be generated and the 3836 \Deleted flag MUST NOT be set for any message. 3838 Because a MOVE applies to a set of messages, it might fail partway 3839 through the set. Regardless of whether the command is successful in 3840 moving the entire set, each individual message SHOULD either be moved 3841 or unaffected. The server MUST leave each message in a state where 3842 it is in at least one of the source or target mailboxes (no message 3843 can be lost or orphaned). The server SHOULD NOT leave any message in 3844 both mailboxes (it would be bad for a partial failure to result in a 3845 bunch of duplicate messages). This is true even if the server 3846 returns a tagged NO response to the command. 3848 Because of the similarity of MOVE to COPY, extensions that affect 3849 COPY affect MOVE in the same way. Response codes such as TRYCREATE 3850 (see Section 7.1), as well as those defined by extensions, are sent 3851 as appropriate. 3853 Servers SHOULD send COPYUID in response to a UID MOVE (see 3854 Section 6.4.9) command. For additional information see Section 7.1. 3856 Servers are also advised to send the COPYUID response code in an 3857 untagged OK before sending EXPUNGE or moved responses. (Sending 3858 COPYUID in the tagged OK, as described in the UIDPLUS specification, 3859 means that clients first receive an EXPUNGE for a message and 3860 afterwards COPYUID for the same message. It can be unnecessarily 3861 difficult to process that sequence usefully.) 3863 An example: 3864 C: a UID MOVE 42:69 foo 3865 S: * OK [COPYUID 432432 42:69 1202:1229] 3866 S: * 22 EXPUNGE 3867 S: (more expunges) 3868 S: a OK Done 3870 Note that the server may send unrelated EXPUNGE responses as well, if 3871 any happen to have been expunged at the same time; this is normal 3872 IMAP operation. 3874 Note that moving a message to the currently selected mailbox (that 3875 is, where the source and target mailboxes are the same) is allowed 3876 when copying the message to the currently selected mailbox is 3877 allowed. 3879 The server may send EXPUNGE responses before the tagged response, so 3880 the client cannot safely send more commands with message sequence 3881 number arguments while the server is processing MOVE. 3883 MOVE and UID MOVE can be pipelined with other commands, but care has 3884 to be taken. Both commands modify sequence numbers and also allow 3885 unrelated EXPUNGE responses. The renumbering of other messages in 3886 the source mailbox following any EXPUNGE response can be surprising 3887 and makes it unsafe to pipeline any command that relies on message 3888 sequence numbers after a MOVE or UID MOVE. Similarly, MOVE cannot be 3889 pipelined with a command that might cause message renumbering. See 3890 Section 5.5, for more information about ambiguities as well as 3891 handling requirements for both clients and servers. 3893 6.4.9. UID Command 3895 Arguments: command name 3896 command arguments 3898 Responses: untagged responses: FETCH, ESEARCH, EXPUNGE 3900 Result: OK - UID command completed 3901 NO - UID command error 3902 BAD - command unknown or arguments invalid 3904 The UID command has three forms. In the first form, it takes as its 3905 arguments a COPY, MOVE, FETCH, or STORE command with arguments 3906 appropriate for the associated command. However, the numbers in the 3907 sequence set argument are unique identifiers instead of message 3908 sequence numbers. Sequence set ranges are permitted, but there is no 3909 guarantee that unique identifiers will be contiguous. 3911 A non-existent unique identifier is ignored without any error message 3912 generated. Thus, it is possible for a UID FETCH command to return an 3913 OK without any data or a UID COPY, UID MOVE or UID STORE to return an 3914 OK without performing any operations. 3916 In the second form, the UID command takes an EXPUNGE command with an 3917 extra parameter the specified a sequence set of UIDs to operate on. 3918 The UID EXPUNGE command permanently removes all messages that both 3919 have the \Deleted flag set and have a UID that is included in the 3920 specified sequence set from the currently selected mailbox. If a 3921 message either does not have the \Deleted flag set or has a UID that 3922 is not included in the specified sequence set, it is not affected. 3924 UID EXPUNGE is particularly useful for disconnected use clients. 3925 By using UID EXPUNGE instead of EXPUNGE when resynchronizing with 3926 the server, the client can ensure that it does not inadvertantly 3927 remove any messages that have been marked as \Deleted by other 3928 clients between the time that the client was last connected and 3929 the time the client resynchronizes. 3931 Example: C: A003 UID EXPUNGE 3000:3002 3932 S: * 3 EXPUNGE 3933 S: * 3 EXPUNGE 3934 S: * 3 EXPUNGE 3935 S: A003 OK UID EXPUNGE completed 3937 In the third form, the UID command takes a SEARCH command with SEARCH 3938 command arguments. The interpretation of the arguments is the same 3939 as with SEARCH; however, the numbers returned in a ESEARCH response 3940 for a UID SEARCH command are unique identifiers instead of message 3941 sequence numbers. Also, the corresponding ESEARCH response MUST 3942 include the UID indicator. For example, the command UID SEARCH 1:100 3943 UID 443:557 returns the unique identifiers corresponding to the 3944 intersection of two sequence sets, the message sequence number range 3945 1:100 and the UID range 443:557. 3947 Note: in the above example, the UID range 443:557 appears. The 3948 same comment about a non-existent unique identifier being ignored 3949 without any error message also applies here. Hence, even if 3950 neither UID 443 or 557 exist, this range is valid and would 3951 include an existing UID 495. 3953 Also note that a UID range of 559:* always includes the UID of the 3954 last message in the mailbox, even if 559 is higher than any 3955 assigned UID value. This is because the contents of a range are 3956 independent of the order of the range endpoints. Thus, any UID 3957 range with * as one of the endpoints indicates at least one 3958 message (the message with the highest numbered UID), unless the 3959 mailbox is empty. 3961 The number after the "*" in an untagged FETCH or EXPUNGE response is 3962 always a message sequence number, not a unique identifier, even for a 3963 UID command response. However, server implementations MUST 3964 implicitly include the UID message data item as part of any FETCH 3965 response caused by a UID command, regardless of whether a UID was 3966 specified as a message data item to the FETCH. 3968 Note: The rule about including the UID message data item as part of a 3969 FETCH response primarily applies to the UID FETCH and UID STORE 3970 commands, including a UID FETCH command that does not include UID as 3971 a message data item. Although it is unlikely that the other UID 3972 commands will cause an untagged FETCH, this rule applies to these 3973 commands as well. 3975 Example: C: A999 UID FETCH 4827313:4828442 FLAGS 3976 S: * 23 FETCH (FLAGS (\Seen) UID 4827313) 3977 S: * 24 FETCH (FLAGS (\Seen) UID 4827943) 3978 S: * 25 FETCH (FLAGS (\Seen) UID 4828442) 3979 S: A999 OK UID FETCH completed 3981 6.5. Client Commands - Experimental/Expansion 3983 6.5.1. X Command 3985 Arguments: implementation defined 3987 Responses: implementation defined 3989 Result: OK - command completed 3990 NO - failure 3991 BAD - command unknown or arguments invalid 3993 Any command prefixed with an X is an experimental command. Commands 3994 which are not part of this specification, a standard or standards- 3995 track revision of this specification, or an IESG-approved 3996 experimental protocol, MUST use the X prefix. 3998 Any added untagged responses issued by an experimental command MUST 3999 also be prefixed with an X. Server implementations MUST NOT send any 4000 such untagged responses, unless the client requested it by issuing 4001 the associated experimental command. 4003 Example: C: a441 CAPABILITY 4004 S: * CAPABILITY IMAP4rev2 XPIG-LATIN 4005 S: a441 OK CAPABILITY completed 4006 C: A442 XPIG-LATIN 4007 S: * XPIG-LATIN ow-nay eaking-spay ig-pay atin-lay 4008 S: A442 OK XPIG-LATIN ompleted-cay 4010 7. Server Responses 4012 Server responses are in three forms: status responses, server data, 4013 and command continuation request. The information contained in a 4014 server response, identified by "Contents:" in the response 4015 descriptions below, is described by function, not by syntax. The 4016 precise syntax of server responses is described in the Formal Syntax 4017 section. 4019 The client MUST be prepared to accept any response at all times. 4021 Status responses can be tagged or untagged. Tagged status responses 4022 indicate the completion result (OK, NO, or BAD status) of a client 4023 command, and have a tag matching the command. 4025 Some status responses, and all server data, are untagged. An 4026 untagged response is indicated by the token "*" instead of a tag. 4027 Untagged status responses indicate server greeting, or server status 4028 that does not indicate the completion of a command (for example, an 4029 impending system shutdown alert). For historical reasons, untagged 4030 server data responses are also called "unsolicited data", although 4031 strictly speaking, only unilateral server data is truly 4032 "unsolicited". 4034 Certain server data MUST be recorded by the client when it is 4035 received; this is noted in the description of that data. Such data 4036 conveys critical information which affects the interpretation of all 4037 subsequent commands and responses (e.g., updates reflecting the 4038 creation or destruction of messages). 4040 Other server data SHOULD be recorded for later reference; if the 4041 client does not need to record the data, or if recording the data has 4042 no obvious purpose (e.g., a SEARCH response when no SEARCH command is 4043 in progress), the data SHOULD be ignored. 4045 An example of unilateral untagged server data occurs when the IMAP 4046 connection is in the selected state. In the selected state, the 4047 server checks the mailbox for new messages as part of command 4048 execution. Normally, this is part of the execution of every command; 4049 hence, a NOOP command suffices to check for new messages. If new 4050 messages are found, the server sends untagged EXISTS response 4051 reflecting the new size of the mailbox. Server implementations that 4052 offer multiple simultaneous access to the same mailbox SHOULD also 4053 send appropriate unilateral untagged FETCH and EXPUNGE responses if 4054 another agent changes the state of any message flags or expunges any 4055 messages. 4057 Command continuation request responses use the token "+" instead of a 4058 tag. These responses are sent by the server to indicate acceptance 4059 of an incomplete client command and readiness for the remainder of 4060 the command. 4062 7.1. Server Responses - Status Responses 4064 Status responses are OK, NO, BAD, PREAUTH and BYE. OK, NO, and BAD 4065 can be tagged or untagged. PREAUTH and BYE are always untagged. 4067 Status responses MAY include an OPTIONAL "response code". A response 4068 code consists of data inside square brackets in the form of an atom, 4069 possibly followed by a space and arguments. The response code 4070 contains additional information or status codes for client software 4071 beyond the OK/NO/BAD condition, and are defined when there is a 4072 specific action that a client can take based upon the additional 4073 information. 4075 The currently defined response codes are: 4077 ALERT The human-readable text contains a special alert that MUST be 4078 presented to the user in a fashion that calls the user's attention 4079 to the message. 4081 ALREADYEXISTS 4083 The operation attempts to create something that already exists, 4084 such as when the CREATE or RENAME directories attempt to create 4085 a mailbox and there is already one of that name. 4087 C: o RENAME this that 4088 S: o NO [ALREADYEXISTS] Mailbox "that" already exists 4090 APPENDUID 4092 Followed by the UIDVALIDITY of the destination mailbox and the 4093 UID assigned to the appended message in the destination 4094 mailbox, indicates that the message has been appended to the 4095 destination mailbox with that UID. 4097 If the server also supports the [MULTIAPPEND] extension, and if 4098 multiple messages were appended in the APPEND command, then the 4099 second value is a UID set containing the UIDs assigned to the 4100 appended messages, in the order they were transmitted in the 4101 APPEND command. This UID set may not contain extraneous UIDs 4102 or the symbol "*". 4104 Note: the UID set form of the APPENDUID response code MUST 4105 NOT be used if only a single message was appended. In 4106 particular, a server MUST NOT send a range such as 123:123. 4107 This is because a client that does not support [MULTIAPPEND] 4108 expects only a single UID and not a UID set. 4110 UIDs are assigned in strictly ascending order in the mailbox 4111 (refer to Section 2.3.1.1); note that a range of 12:10 is 4112 exactly equivalent to 10:12 and refers to the sequence 4113 10,11,12. 4115 This response code is returned in a tagged OK response to the 4116 APPEND command. 4118 AUTHENTICATIONFAILED 4120 Authentication failed for some reason on which the server is 4121 unwilling to elaborate. Typically, this includes "unknown 4122 user" and "bad password". 4124 This is the same as not sending any response code, except that 4125 when a client sees AUTHENTICATIONFAILED, it knows that the 4126 problem wasn't, e.g., UNAVAILABLE, so there's no point in 4127 trying the same login/password again later. 4129 C: b LOGIN "fred" "foo" 4130 S: b NO [AUTHENTICATIONFAILED] Authentication failed 4132 AUTHORIZATIONFAILED Authentication succeeded in using the 4133 authentication identity, but the server cannot or will not allow 4134 the authentication identity to act as the requested authorization 4135 identity. This is only applicable when the authentication and 4136 authorization identities are different. C: c1 AUTHENTICATE PLAIN 4137 [...] 4138 S: c1 NO [AUTHORIZATIONFAILED] No such authorization-ID 4139 C: c2 AUTHENTICATE PLAIN 4140 [...] 4141 S: c2 NO [AUTHORIZATIONFAILED] Authenticator is not an admin 4143 BADCHARSET Optionally followed by a parenthesized list of charsets. 4144 A SEARCH failed because the given charset is not supported by this 4145 implementation. If the optional list of charsets is given, this 4146 lists the charsets that are supported by this implementation. 4148 CANNOT 4150 The operation violates some invariant of the server and can 4151 never succeed. 4153 C: l create "///////" 4154 S: l NO [CANNOT] Adjacent slashes are not supported 4156 CAPABILITY Followed by a list of capabilities. This can appear in 4157 the initial OK or PREAUTH response to transmit an initial 4158 capabilities list. It can also appear in tagged responses to 4159 LOGIN or AUTHENTICATE commands. This makes it unnecessary for a 4160 client to send a separate CAPABILITY command if it recognizes this 4161 response. 4163 CLIENTBUG 4165 The server has detected a client bug. This can accompany all 4166 of OK, NO, and BAD, depending on what the client bug is. 4168 C: k1 select "/archive/projects/experiment-iv" 4169 [...] 4170 S: k1 OK [READ-ONLY] Done 4171 C: k2 status "/archive/projects/experiment-iv" (messages) 4172 [...] 4173 S: k2 OK [CLIENTBUG] Done 4175 CLOSED 4177 The CLOSED response code has no parameters. A server return 4178 the CLOSED response code when the currently selected mailbox is 4179 closed implicitly using the SELECT/EXAMINE command on another 4180 mailbox. The CLOSED response code serves as a boundary between 4181 responses for the previously opened mailbox (which was closed) 4182 and the newly selected mailbox; all responses before the CLOSED 4183 response code relate to the mailbox that was closed, and all 4184 subsequent responses relate to the newly opened mailbox. 4186 There is no need to return the CLOSED response code on 4187 completion of the CLOSE or the UNSELECT command (or similar), 4188 whose purpose is to close the currently selected mailbox 4189 without opening a new one. 4191 The server can also return an unsolicited CLOSED response code 4192 when it wants to force the client to return to authenticated 4193 state. For example, the server can do that when the mailbox 4194 requires repairs or is deleted in another session. 4196 CONTACTADMIN 4198 The user should contact the system administrator or support 4199 desk. 4201 C: e login "fred" "foo" 4202 S: e OK [CONTACTADMIN] 4204 COPYUID 4206 Followed by the UIDVALIDITY of the destination mailbox, a UID 4207 set containing the UIDs of the message(s) in the source mailbox 4208 that were copied to the destination mailbox and containing the 4209 UIDs assigned to the copied message(s) in the destination 4210 mailbox, indicates that the message(s) have been copied to the 4211 destination mailbox with the stated UID(s). 4213 The source UID set is in the order the message(s) were copied; 4214 the destination UID set corresponds to the source UID set and 4215 is in the same order. Neither of the UID sets may contain 4216 extraneous UIDs or the symbol "*". 4218 UIDs are assigned in strictly ascending order in the mailbox 4219 (refer to Section 2.3.1.1); note that a range of 12:10 is 4220 exactly equivalent to 10:12 and refers to the sequence 4221 10,11,12. 4223 This response code is returned in a tagged OK response to the 4224 COPY command. 4226 CORRUPTION 4228 The server discovered that some relevant data (e.g., the 4229 mailbox) are corrupt. This response code does not include any 4230 information about what's corrupt, but the server can write that 4231 to its logfiles. 4233 C: i select "/archive/projects/experiment-iv" 4234 S: i NO [CORRUPTION] Cannot open mailbox 4236 EXPIRED 4238 Either authentication succeeded or the server no longer had the 4239 necessary data; either way, access is no longer permitted using 4240 that passphrase. The client or user should get a new 4241 passphrase. 4243 C: d login "fred" "foo" 4244 S: d NO [EXPIRED] That password isn't valid any more 4246 EXPUNGEISSUED 4248 Someone else has issued an EXPUNGE for the same mailbox. The 4249 client may want to issue NOOP soon. [IMAP-MULTIACCESS] 4250 discusses this subject in depth. 4252 C: h search from fred@example.com 4253 S: * SEARCH 1 2 3 5 8 13 21 42 4254 S: h OK [EXPUNGEISSUED] Search completed 4256 INUSE 4257 An operation has not been carried out because it involves 4258 sawing off a branch someone else is sitting on. Someone else 4259 may be holding an exclusive lock needed for this operation, or 4260 the operation may involve deleting a resource someone else is 4261 using, typically a mailbox. 4263 The operation may succeed if the client tries again later. 4265 C: g delete "/archive/projects/experiment-iv" 4266 S: g NO [INUSE] Mailbox in use 4268 LIMIT 4270 The operation ran up against an implementation limit of some 4271 kind, such as the number of flags on a single message or the 4272 number of flags used in a mailbox. 4274 C: m STORE 42 FLAGS f1 f2 f3 f4 f5 ... f250 4275 S: m NO [LIMIT] At most 32 flags in one mailbox supported 4277 NONEXISTENT 4279 The operation attempts to delete something that does not exist. 4280 Similar to ALREADYEXISTS. 4282 C: p RENAME this that 4283 S: p NO [NONEXISTENT] No such mailbox 4285 NOPERM 4287 The access control system (e.g., Access Control List (ACL), see 4288 [RFC4314] does not permit this user to carry out an operation, 4289 such as selecting or creating a mailbox. 4291 C: f select "/archive/projects/experiment-iv" 4292 S: f NO [NOPERM] Access denied 4294 OVERQUOTA 4296 The user would be over quota after the operation. (The user 4297 may or may not be over quota already.) 4299 Note that if the server sends OVERQUOTA but doesn't support the 4300 IMAP QUOTA extension defined by [RFC2087], then there is a 4301 quota, but the client cannot find out what the quota is. 4303 C: n1 uid copy 1:* oldmail 4304 S: n1 NO [OVERQUOTA] Sorry 4305 C: n2 uid copy 1:* oldmail 4306 S: n2 OK [OVERQUOTA] You are now over your soft quota 4308 PARSE The human-readable text represents an error in parsing the 4309 [RFC-5322] header or [MIME-IMB] headers of a message in the 4310 mailbox. 4312 PERMANENTFLAGS Followed by a parenthesized list of flags, indicates 4313 which of the known flags the client can change permanently. Any 4314 flags that are in the FLAGS untagged response, but not the 4315 PERMANENTFLAGS list, can not be set permanently. The 4316 PERMANENTFLAGS list can also include the special flag \*, which 4317 indicates that it is possible to create new keywords by attempting 4318 to store those keywords in the mailbox. If the client attempts to 4319 STORE a flag that is not in the PERMANENTFLAGS list, the server 4320 will either ignore the change or store the state change for the 4321 remainder of the current session only. 4322 There is no need for a server that included the special flag \* to 4323 return a new PERMANENTFLAGS response code when a new keyword was 4324 successfully set on a message upon client request. However if the 4325 server has a limit on the number of different keywords that can be 4326 stored in a mailbox and that limit is reached, the server MUST 4327 send a new PERMANENTFLAGS response code without the special flag 4328 \*. 4330 PRIVACYREQUIRED 4332 The operation is not permitted due to a lack of privacy. If 4333 Transport Layer Security (TLS) is not in use, the client could 4334 try STARTTLS (see Section 6.2.1) and then repeat the operation. 4336 C: d login "fred" "foo" 4337 S: d NO [PRIVACYREQUIRED] Connection offers no privacy 4339 C: d select inbox 4340 S: d NO [PRIVACYREQUIRED] Connection offers no privacy 4342 READ-ONLY The mailbox is selected read-only, or its access while 4343 selected has changed from read-write to read-only. 4345 READ-WRITE The mailbox is selected read-write, or its access while 4346 selected has changed from read-only to read-write. 4348 SERVERBUG 4350 The server encountered a bug in itself or violated one of its 4351 own invariants. 4353 C: j select "/archive/projects/experiment-iv" 4354 S: j NO [SERVERBUG] This should not happen 4356 TRYCREATE An APPEND or COPY attempt is failing because the target 4357 mailbox does not exist (as opposed to some other reason). This is 4358 a hint to the client that the operation can succeed if the mailbox 4359 is first created by the CREATE command. 4361 UIDNEXT Followed by a decimal number, indicates the next unique 4362 identifier value. Refer to Section 2.3.1.1 for more information. 4364 UIDNOTSTICKY 4366 The selected mailbox is supported by a mail store that does not 4367 support persistent UIDs; that is, UIDVALIDITY will be different 4368 each time the mailbox is selected. Consequently, APPEND or 4369 COPY to this mailbox will not return an APPENDUID or COPYUID 4370 response code. 4372 This response code is returned in an untagged NO response to 4373 the SELECT command. 4375 Note: servers SHOULD NOT have any UIDNOTSTICKY mail stores. 4376 This facility exists to support legacy mail stores in which 4377 it is technically infeasible to support persistent UIDs. 4378 This should be avoided when designing new mail stores. 4380 UIDVALIDITY Followed by a decimal number, indicates the unique 4381 identifier validity value. Refer to Section 2.3.1.1 for more 4382 information. 4384 UNAVAILABLE 4386 Temporary failure because a subsystem is down. For example, an 4387 IMAP server that uses a Lightweight Directory Access Protocol 4388 (LDAP) or Radius server for authentication might use this 4389 response code when the LDAP/Radius server is down. 4391 C: a LOGIN "fred" "foo" 4392 S: a NO [UNAVAILABLE] User's backend down for maintenance 4394 UNKNOWN-CTE 4396 The server does not know how to decode the section's Content- 4397 Transfer-Encoding. 4399 Additional response codes defined by particular client or server 4400 implementations SHOULD be prefixed with an "X" until they are added 4401 to a revision of this protocol. Client implementations SHOULD ignore 4402 response codes that they do not recognize. 4404 7.1.1. OK Response 4406 Contents: OPTIONAL response code 4407 human-readable text 4409 The OK response indicates an information message from the server. 4410 When tagged, it indicates successful completion of the associated 4411 command. The human-readable text MAY be presented to the user as an 4412 information message. The untagged form indicates an information-only 4413 message; the nature of the information MAY be indicated by a response 4414 code. 4416 The untagged form is also used as one of three possible greetings at 4417 connection startup. It indicates that the connection is not yet 4418 authenticated and that a LOGIN or an AUTHENTICATE command is needed. 4420 Example: S: * OK IMAP4rev2 server ready 4421 C: A001 LOGIN fred blurdybloop 4422 S: * OK [ALERT] System shutdown in 10 minutes 4423 S: A001 OK LOGIN Completed 4425 7.1.2. NO Response 4427 Contents: OPTIONAL response code 4428 human-readable text 4430 The NO response indicates an operational error message from the 4431 server. When tagged, it indicates unsuccessful completion of the 4432 associated command. The untagged form indicates a warning; the 4433 command can still complete successfully. The human-readable text 4434 describes the condition. 4436 Example: C: A222 COPY 1:2 owatagusiam 4437 S: * NO Disk is 98% full, please delete unnecessary data 4438 S: A222 OK COPY completed 4439 C: A223 COPY 3:200 blurdybloop 4440 S: * NO Disk is 98% full, please delete unnecessary data 4441 S: * NO Disk is 99% full, please delete unnecessary data 4442 S: A223 NO COPY failed: disk is full 4444 7.1.3. BAD Response 4446 Contents: OPTIONAL response code 4447 human-readable text 4449 The BAD response indicates an error message from the server. When 4450 tagged, it reports a protocol-level error in the client's command; 4451 the tag indicates the command that caused the error. The untagged 4452 form indicates a protocol-level error for which the associated 4453 command can not be determined; it can also indicate an internal 4454 server failure. The human-readable text describes the condition. 4456 Example: C: ...very long command line... 4457 S: * BAD Command line too long 4458 C: ...empty line... 4459 S: * BAD Empty command line 4460 C: A443 EXPUNGE 4461 S: * BAD Disk crash, attempting salvage to a new disk! 4462 S: * OK Salvage successful, no data lost 4463 S: A443 OK Expunge completed 4465 7.1.4. PREAUTH Response 4467 Contents: OPTIONAL response code 4468 human-readable text 4470 The PREAUTH response is always untagged, and is one of three possible 4471 greetings at connection startup. It indicates that the connection 4472 has already been authenticated by external means; thus no LOGIN/ 4473 AUTHENTICATE command is needed. 4475 Example: S: * PREAUTH IMAP4rev2 server logged in as Smith 4477 7.1.5. BYE Response 4479 Contents: OPTIONAL response code 4480 human-readable text 4482 The BYE response is always untagged, and indicates that the server is 4483 about to close the connection. The human-readable text MAY be 4484 displayed to the user in a status report by the client. The BYE 4485 response is sent under one of four conditions: 4487 1. as part of a normal logout sequence. The server will close the 4488 connection after sending the tagged OK response to the LOGOUT 4489 command. 4491 2. as a panic shutdown announcement. The server closes the 4492 connection immediately. 4494 3. as an announcement of an inactivity autologout. The server 4495 closes the connection immediately. 4497 4. as one of three possible greetings at connection startup, 4498 indicating that the server is not willing to accept a connection 4499 from this client. The server closes the connection immediately. 4501 The difference between a BYE that occurs as part of a normal LOGOUT 4502 sequence (the first case) and a BYE that occurs because of a failure 4503 (the other three cases) is that the connection closes immediately in 4504 the failure case. In all cases the client SHOULD continue to read 4505 response data from the server until the connection is closed; this 4506 will ensure that any pending untagged or completion responses are 4507 read and processed. 4509 Example: S: * BYE Autologout; idle for too long 4511 7.2. Server Responses - Server and Mailbox Status 4513 These responses are always untagged. This is how server and mailbox 4514 status data are transmitted from the server to the client. Many of 4515 these responses typically result from a command with the same name. 4517 7.2.1. The ENABLED Response 4519 Contents: capability listing 4521 The ENABLED response occurs as a result of an ENABLE command. The 4522 capability listing contains a space-separated listing of capability 4523 names that the server supports and that were successfully enabled. 4524 The ENABLED response may contain no capabilities, which means that no 4525 extensions listed by the client were successfully enabled. 4527 7.2.2. CAPABILITY Response 4529 Contents: capability listing 4531 The CAPABILITY response occurs as a result of a CAPABILITY command. 4532 The capability listing contains a space-separated listing of 4533 capability names that the server supports. The capability listing 4534 MUST include the atom "IMAP4rev2". 4536 In addition, client and server implementations MUST implement the 4537 STARTTLS, LOGINDISABLED, and AUTH=PLAIN (described in [PLAIN]) 4538 capabilities. See the Security Considerations section for important 4539 information. 4541 A capability name which begins with "AUTH=" indicates that the server 4542 supports that particular authentication mechanism. 4544 The LOGINDISABLED capability indicates that the LOGIN command is 4545 disabled, and that the server will respond with a tagged NO response 4546 to any attempt to use the LOGIN command even if the user name and 4547 password are valid. An IMAP client MUST NOT issue the LOGIN command 4548 if the server advertises the LOGINDISABLED capability. 4550 Other capability names indicate that the server supports an 4551 extension, revision, or amendment to the IMAP4rev2 protocol. Server 4552 responses MUST conform to this document until the client issues a 4553 command that uses the associated capability. 4555 Capability names MUST either begin with "X" or be standard or 4556 standards-track IMAP4rev2 extensions, revisions, or amendments 4557 registered with IANA. A server MUST NOT offer unregistered or non- 4558 standard capability names, unless such names are prefixed with an 4559 "X". 4561 Client implementations SHOULD NOT require any capability name other 4562 than "IMAP4rev2", and MUST ignore any unknown capability names. 4564 A server MAY send capabilities automatically, by using the CAPABILITY 4565 response code in the initial PREAUTH or OK responses, and by sending 4566 an updated CAPABILITY response code in the tagged OK response as part 4567 of a successful authentication. It is unnecessary for a client to 4568 send a separate CAPABILITY command if it recognizes these automatic 4569 capabilities. 4571 Example: S: * CAPABILITY IMAP4rev2 STARTTLS AUTH=GSSAPI XPIG-LATIN 4573 7.2.3. LIST Response 4575 Contents: name attributes 4576 hierarchy delimiter 4577 name 4579 The LIST response occurs as a result of a LIST command. It returns a 4580 single name that matches the LIST specification. There can be 4581 multiple LIST responses for a single LIST command. 4583 The following base name attributes are defined: 4585 \Noinferiors It is not possible for any child levels of hierarchy to 4586 exist under this name; no child levels exist now and none can be 4587 created in the future. 4589 \Noselect It is not possible to use this name as a selectable 4590 mailbox. 4592 \HasChildren The presence of this attribute indicates that the 4593 mailbox has child mailboxes. A server SHOULD NOT set this 4594 attribute if there are child mailboxes and the user does not have 4595 permission to access any of them. In this case, \HasNoChildren 4596 SHOULD be used. In many cases, however, a server may not be able 4597 to efficiently compute whether a user has access to any child 4598 mailbox. Note that even though the \HasChildren attribute for a 4599 mailbox must be correct at the time of processing of the mailbox, 4600 a client must be prepared to deal with a situation when a mailbox 4601 is marked with the \HasChildren attribute, but no child mailbox 4602 appears in the response to the LIST command. This might happen, 4603 for example, due to children mailboxes being deleted or made 4604 inaccessible to the user (using access control) by another client 4605 before the server is able to list them. 4607 \HasNoChildren The presence of this attribute indicates that the 4608 mailbox has NO child mailboxes that are accessible to the 4609 currently authenticated user. 4611 \Marked The mailbox has been marked "interesting" by the server; the 4612 mailbox probably contains messages that have been added since the 4613 last time the mailbox was selected. 4615 \Unmarked The mailbox does not contain any additional messages since 4616 the last time the mailbox was selected. 4618 It is an error for the server to return both a \HasChildren and a 4619 \HasNoChildren attribute in the same LIST response. 4621 Note: the \HasNoChildren attribute should not be confused with the 4622 \NoInferiors attribute, which indicates that no child mailboxes 4623 exist now and none can be created in the future. 4625 If it is not feasible for the server to determine whether or not the 4626 mailbox is "interesting", the server SHOULD NOT send either \Marked 4627 or \Unmarked. The server MUST NOT send more than one of \Marked, 4628 \Unmarked, and \Noselect for a single mailbox, and MAY send none of 4629 these. 4631 In addition to the base name attributes defined above, an IMAP server 4632 MAY also include any or all of the following attributes that denote 4633 "role" (or "special-use") of a mailbox. These attributes are 4634 included along with base attributes defined above. A given mailbox 4635 may have none, one, or more than one of these attributes. In some 4636 cases, a special use is advice to a client about what to put in that 4637 mailbox. In other cases, it's advice to a client about what to 4638 expect to find there. 4640 \All This mailbox presents all messages in the user's message store. 4641 Implementations MAY omit some messages, such as, perhaps, those in 4642 \Trash and \Junk. When this special use is supported, it is 4643 almost certain to represent a virtual mailbox. 4645 \Archive This mailbox is used to archive messages. The meaning of 4646 an "archival" mailbox is server-dependent; typically, it will be 4647 used to get messages out of the inbox, or otherwise keep them out 4648 of the user's way, while still making them accessible. 4650 \Drafts This mailbox is used to hold draft messages -- typically, 4651 messages that are being composed but have not yet been sent. In 4652 some server implementations, this might be a virtual mailbox, 4653 containing messages from other mailboxes that are marked with the 4654 "\Draft" message flag. Alternatively, this might just be advice 4655 that a client put drafts here. 4657 \Flagged This mailbox presents all messages marked in some way as 4658 "important". When this special use is supported, it is likely to 4659 represent a virtual mailbox collecting messages (from other 4660 mailboxes) that are marked with the "\Flagged" message flag. 4662 \Junk This mailbox is where messages deemed to be junk mail are 4663 held. Some server implementations might put messages here 4664 automatically. Alternatively, this might just be advice to a 4665 client-side spam filter. 4667 \Sent This mailbox is used to hold copies of messages that have been 4668 sent. Some server implementations might put messages here 4669 automatically. Alternatively, this might just be advice that a 4670 client save sent messages here. 4672 \Trash This mailbox is used to hold messages that have been deleted 4673 or marked for deletion. In some server implementations, this 4674 might be a virtual mailbox, containing messages from other 4675 mailboxes that are marked with the "\Deleted" message flag. 4676 Alternatively, this might just be advice that a client that 4677 chooses not to use the IMAP "\Deleted" model should use this as 4678 its trash location. In server implementations that strictly 4679 expect the IMAP "\Deleted" model, this special use is likely not 4680 to be supported. 4682 All of special-use attributes are OPTIONAL, and any given server or 4683 message store may support any combination of the attributes, or none 4684 at all. In most cases, there will likely be at most one mailbox with 4685 a given attribute for a given user, but in some server or message 4686 store implementations it might be possible for multiple mailboxes to 4687 have the same special-use attribute. 4689 Special-use attributes are likely to be user-specific. User Adam 4690 might share his \Sent mailbox with user Barb, but that mailbox is 4691 unlikely to also serve as Barb's \Sent mailbox. 4693 The hierarchy delimiter is a character used to delimit levels of 4694 hierarchy in a mailbox name. A client can use it to create child 4695 mailboxes, and to search higher or lower levels of naming hierarchy. 4696 All children of a top-level hierarchy node MUST use the same 4697 separator character. A NIL hierarchy delimiter means that no 4698 hierarchy exists; the name is a "flat" name. 4700 The name represents an unambiguous left-to-right hierarchy, and MUST 4701 be valid for use as a reference in LIST and LSUB commands. Unless 4702 \Noselect is indicated, the name MUST also be valid as an argument 4703 for commands, such as SELECT, that accept mailbox names. 4705 Example: S: * LIST (\Noselect) "/" ~/Mail/foo 4707 7.2.4. LSUB Response 4709 Contents: name attributes 4710 hierarchy delimiter 4711 name 4713 The LSUB response occurs as a result of an LSUB command. It returns 4714 a single name that matches the LSUB specification. There can be 4715 multiple LSUB responses for a single LSUB command. The data is 4716 identical in format to the LIST response. 4718 Example: S: * LSUB () "." #news.comp.mail.misc 4720 7.2.5. NAMESPACE Response 4722 Contents: the prefix and hierarchy delimiter to the server's 4723 Personal Namespace(s), Other Users' Namespace(s), and 4724 Shared Namespace(s) 4726 The NAMESPACE response occurs as a result of a NAMESPACE command. It 4727 contains the prefix and hierarchy delimiter to the server's Personal 4728 Namespace(s), Other Users' Namespace(s), and Shared Namespace(s) that 4729 the server wishes to expose. The response will contain a NIL for any 4730 namespace class that is not available. Namespace-Response-Extensions 4731 ABNF non terminal is defined for extensibility and MAY be included in 4732 the response. Namespace-Response-Extensions which are not on the 4733 IETF standards track, MUST be prefixed with an "X-". 4735 Example: S: * NAMESPACE (("" "/")) (("~" "/")) NIL 4737 7.2.6. STATUS Response 4739 Contents: name 4740 status parenthesized list 4742 The STATUS response occurs as a result of an STATUS command. It 4743 returns the mailbox name that matches the STATUS specification and 4744 the requested mailbox status information. 4746 Example: S: * STATUS blurdybloop (MESSAGES 231 UIDNEXT 44292) 4748 7.2.7. ESEARCH Response 4750 Contents: one or more search-return-data pairs 4752 The ESEARCH response occurs as a result of a SEARCH or UID SEARCH 4753 command. 4755 The ESEARCH response starts with an optional search correlator. If 4756 it is missing, then the response was not caused by a particular IMAP 4757 command, whereas if it is present, it contains the tag of the command 4758 that caused the response to be returned. 4760 The search correlator is followed by an optional UID indicator. If 4761 this indicator is present, all data in the ESEARCH response refers to 4762 UIDs, otherwise all returned data refers to message numbers. 4764 The rest of the ESEARCH response contains one or more search data 4765 pairs. Each pair starts with unique return item name, followed by a 4766 space and the corresponding data. Search data pairs may be returned 4767 in any order. Unless specified otherwise by an extension, any return 4768 item name SHOULD appear only once in an ESEARCH response. 4770 [[TBD: describe the most common search data pairs returned.]] 4772 Example: S: * ESEARCH UID COUNT 5 ALL 4:19,21,28 4774 Example: S: * ESEARCH (TAG "a567") UID COUNT 5 ALL 4:19,21,28 4776 Example: S: * ESEARCH COUNT 5 ALL 1:17,21 4778 7.2.8. FLAGS Response 4780 Contents: flag parenthesized list 4782 The FLAGS response occurs as a result of a SELECT or EXAMINE command. 4783 The flag parenthesized list identifies the flags (at a minimum, the 4784 system-defined flags) that are applicable for this mailbox. Flags 4785 other than the system flags can also exist, depending on server 4786 implementation. 4788 The update from the FLAGS response MUST be recorded by the client. 4790 Example: S: * FLAGS (\Answered \Flagged \Deleted \Seen \Draft) 4792 7.3. Server Responses - Mailbox Size 4794 These responses are always untagged. This is how changes in the size 4795 of the mailbox are transmitted from the server to the client. 4796 Immediately following the "*" token is a number that represents a 4797 message count. 4799 7.3.1. EXISTS Response 4801 Contents: none 4803 The EXISTS response reports the number of messages in the mailbox. 4804 This response occurs as a result of a SELECT or EXAMINE command, and 4805 if the size of the mailbox changes (e.g., new messages). 4807 The update from the EXISTS response MUST be recorded by the client. 4809 Example: S: * 23 EXISTS 4811 7.4. Server Responses - Message Status 4813 These responses are always untagged. This is how message data are 4814 transmitted from the server to the client, often as a result of a 4815 command with the same name. Immediately following the "*" token is a 4816 number that represents a message sequence number. 4818 7.4.1. EXPUNGE Response 4820 Contents: none 4822 The EXPUNGE response reports that the specified message sequence 4823 number has been permanently removed from the mailbox. The message 4824 sequence number for each successive message in the mailbox is 4825 immediately decremented by 1, and this decrement is reflected in 4826 message sequence numbers in subsequent responses (including other 4827 untagged EXPUNGE responses). 4829 The EXPUNGE response also decrements the number of messages in the 4830 mailbox; it is not necessary to send an EXISTS response with the new 4831 value. 4833 As a result of the immediate decrement rule, message sequence numbers 4834 that appear in a set of successive EXPUNGE responses depend upon 4835 whether the messages are removed starting from lower numbers to 4836 higher numbers, or from higher numbers to lower numbers. For 4837 example, if the last 5 messages in a 9-message mailbox are expunged, 4838 a "lower to higher" server will send five untagged EXPUNGE responses 4839 for message sequence number 5, whereas a "higher to lower server" 4840 will send successive untagged EXPUNGE responses for message sequence 4841 numbers 9, 8, 7, 6, and 5. 4843 An EXPUNGE response MUST NOT be sent when no command is in progress, 4844 nor while responding to a FETCH, STORE, or SEARCH command. This rule 4845 is necessary to prevent a loss of synchronization of message sequence 4846 numbers between client and server. A command is not "in progress" 4847 until the complete command has been received; in particular, a 4848 command is not "in progress" during the negotiation of command 4849 continuation. 4851 Note: UID FETCH, UID STORE, and UID SEARCH are different commands 4852 from FETCH, STORE, and SEARCH. An EXPUNGE response MAY be sent 4853 during a UID command. 4855 The update from the EXPUNGE response MUST be recorded by the client. 4857 Example: S: * 44 EXPUNGE 4859 7.4.2. FETCH Response 4861 Contents: message data 4863 The FETCH response returns data about a message to the client. The 4864 data are pairs of data item names and their values in parentheses. 4865 This response occurs as the result of a FETCH or STORE command, as 4866 well as by unilateral server decision (e.g., flag updates). 4868 The current data items are: 4870 BINARY[]<> 4872 An or expressing the content of the 4873 specified section after removing any Content-Transfer-Encoding- 4874 related encoding. If is present it refers to the 4875 offset within the DECODED section data. 4877 If the domain of the decoded data is "8bit" and the data does 4878 not contain the NUL octet, the server SHOULD return the data in 4879 a instead of a ; this allows the client to 4880 determine if the "8bit" data contains the NUL octet without 4881 having to explicitly scan the data stream for for NULs. 4883 Messaging clients and servers have been notoriously lax in 4884 their adherence to the Internet CRLF convention for terminating 4885 lines of textual data (text/* media types) in Internet 4886 protocols. When sending data in BINARY[...] FETCH data item, 4887 servers MUST ensure that textual line-oriented sections are 4888 always transmitted using the IMAP4 CRLF line termination 4889 syntax, regardless of the underlying storage representation of 4890 the data on the server. 4892 If the server does not know how to decode the section's 4893 Content-Transfer-Encoding, it MUST fail the request and issue a 4894 "NO" response that contains the "UNKNOWN-CTE" response code. 4896 BINARY.SIZE[] 4898 The size of the section after removing any Content-Transfer- 4899 Encoding-related encoding. The value returned MUST match the 4900 size of the or that will be returned by 4901 the corresponding FETCH BINARY request. 4903 If the server does not know how to decode the section's 4904 Content-Transfer-Encoding, it MUST fail the request and issue a 4905 "NO" response that contains the "UNKNOWN-CTE" response code. 4907 BODY A form of BODYSTRUCTURE without extension data. 4909 BODY[
]<> 4911 A string expressing the body contents of the specified section. 4912 The string SHOULD be interpreted by the client according to the 4913 content transfer encoding, body type, and subtype. 4915 If the origin octet is specified, this string is a substring of 4916 the entire body contents, starting at that origin octet. This 4917 means that BODY[]<0> MAY be truncated, but BODY[] is NEVER 4918 truncated. 4920 Note: The origin octet facility MUST NOT be used by a server 4921 in a FETCH response unless the client specifically requested 4922 it by means of a FETCH of a BODY[
]<> data 4923 item. 4925 8-bit textual data is permitted if a [CHARSET] identifier is 4926 part of the body parameter parenthesized list for this section. 4927 Note that headers (part specifiers HEADER or MIME, or the 4928 header portion of a MESSAGE/RFC822 or MESSAGE/GLOBAL part), MAY 4929 be in UTF-8. Note also that the [RFC-5322] delimiting blank 4930 line between the header and the body is not affected by header 4931 line subsetting; the blank line is always included as part of 4932 header data, except in the case of a message which has no body 4933 and no blank line. 4935 Non-textual data such as binary data MUST be transfer encoded 4936 into a textual form, such as BASE64, prior to being sent to the 4937 client. To derive the original binary data, the client MUST 4938 decode the transfer encoded string. 4940 BODYSTRUCTURE 4942 A parenthesized list that describes the [MIME-IMB] body 4943 structure of a message. This is computed by the server by 4944 parsing the [MIME-IMB] header fields, defaulting various fields 4945 as necessary. 4947 For example, a simple text message of 48 lines and 2279 octets 4948 can have a body structure of: ("TEXT" "PLAIN" ("CHARSET" "US- 4949 ASCII") NIL NIL "7BIT" 2279 48) 4951 Multiple parts are indicated by parenthesis nesting. Instead 4952 of a body type as the first element of the parenthesized list, 4953 there is a sequence of one or more nested body structures. The 4954 second element of the parenthesized list is the multipart 4955 subtype (mixed, digest, parallel, alternative, etc.). 4957 For example, a two part message consisting of a text and a 4958 BASE64-encoded text attachment can have a body structure of: 4959 (("TEXT" "PLAIN" ("CHARSET" "US-ASCII") NIL NIL "7BIT" 1152 4960 23)("TEXT" "PLAIN" ("CHARSET" "US-ASCII" "NAME" "cc.diff") 4961 "<960723163407.20117h@cac.washington.edu>" "Compiler diff" 4962 "BASE64" 4554 73) "MIXED") 4964 Extension data follows the multipart subtype. Extension data 4965 is never returned with the BODY fetch, but can be returned with 4966 a BODYSTRUCTURE fetch. Extension data, if present, MUST be in 4967 the defined order. The extension data of a multipart body part 4968 are in the following order: 4970 body parameter parenthesized list A parenthesized list of 4971 attribute/value pairs [e.g., ("foo" "bar" "baz" "rag") where 4972 "bar" is the value of "foo", and "rag" is the value of 4973 "baz"] as defined in [MIME-IMB]. Servers SHOULD decode 4974 parameter value continuations as described in [RFC2231]. 4976 body disposition A parenthesized list, consisting of a 4977 disposition type string, followed by a parenthesized list of 4978 disposition attribute/value pairs as defined in 4979 [DISPOSITION]. Servers SHOULD decode parameter value 4980 continuations as described in [RFC2231]. 4982 body language A string or parenthesized list giving the body 4983 language value as defined in [LANGUAGE-TAGS]. 4985 body location A string giving the body content URI as defined 4986 in [LOCATION]. 4988 Any following extension data are not yet defined in this 4989 version of the protocol. Such extension data can consist of 4990 zero or more NILs, strings, numbers, or potentially nested 4991 parenthesized lists of such data. Client implementations that 4992 do a BODYSTRUCTURE fetch MUST be prepared to accept such 4993 extension data. Server implementations MUST NOT send such 4994 extension data until it has been defined by a revision of this 4995 protocol. 4997 The basic fields of a non-multipart body part are in the 4998 following order: 5000 body type A string giving the content media type name as 5001 defined in [MIME-IMB]. 5003 body subtype A string giving the content subtype name as 5004 defined in [MIME-IMB]. 5006 body parameter parenthesized list A parenthesized list of 5007 attribute/value pairs [e.g., ("foo" "bar" "baz" "rag") where 5008 "bar" is the value of "foo" and "rag" is the value of "baz"] 5009 as defined in [MIME-IMB]. 5011 body id A string giving the Content-ID header field value as 5012 defined in Section 7 of [MIME-IMB]. 5014 body description A string giving the Content-Description 5015 header field value as defined in Section 8 of [MIME-IMB]. 5017 body encoding A string giving the content transfer encoding as 5018 defined in Section 6 of [MIME-IMB]. 5020 body size A number giving the size of the body in octets. 5021 Note that this size is the size in its transfer encoding and 5022 not the resulting size after any decoding. 5024 A body type of type MESSAGE and subtype RFC822 contains, 5025 immediately after the basic fields, the envelope structure, 5026 body structure, and size in text lines of the encapsulated 5027 message. 5029 A body type of type TEXT contains, immediately after the basic 5030 fields, the size of the body in text lines. Note that this 5031 size is the size in its content transfer encoding and not the 5032 resulting size after any decoding. 5034 Extension data follows the basic fields and the type-specific 5035 fields listed above. Extension data is never returned with the 5036 BODY fetch, but can be returned with a BODYSTRUCTURE fetch. 5037 Extension data, if present, MUST be in the defined order. 5039 The extension data of a non-multipart body part are in the 5040 following order: 5042 body MD5 A string giving the body MD5 value as defined in 5043 [MD5]. 5045 body disposition A parenthesized list with the same content 5046 and function as the body disposition for a multipart body 5047 part. 5049 body language A string or parenthesized list giving the body 5050 language value as defined in [LANGUAGE-TAGS]. 5052 body location A string giving the body content URI as defined 5053 in [LOCATION]. 5055 Any following extension data are not yet defined in this 5056 version of the protocol, and would be as described above under 5057 multipart extension data. 5059 ENVELOPE 5061 A parenthesized list that describes the envelope structure of a 5062 message. This is computed by the server by parsing the 5063 [RFC-5322] header into the component parts, defaulting various 5064 fields as necessary. 5066 The fields of the envelope structure are in the following 5067 order: date, subject, from, sender, reply-to, to, cc, bcc, in- 5068 reply-to, and message-id. The date, subject, in-reply-to, and 5069 message-id fields are strings. The from, sender, reply-to, to, 5070 cc, and bcc fields are parenthesized lists of address 5071 structures. 5073 An address structure is a parenthesized list that describes an 5074 electronic mail address. The fields of an address structure 5075 are in the following order: personal name, [SMTP] at-domain- 5076 list (source route), mailbox name, and host name. 5078 [RFC-5322] group syntax is indicated by a special form of 5079 address structure in which the host name field is NIL. If the 5080 mailbox name field is also NIL, this is an end of group marker 5081 (semi-colon in RFC 822 syntax). If the mailbox name field is 5082 non-NIL, this is a start of group marker, and the mailbox name 5083 field holds the group name phrase. 5085 If the Date, Subject, In-Reply-To, and Message-ID header lines 5086 are absent in the [RFC-5322] header, the corresponding member 5087 of the envelope is NIL; if these header lines are present but 5088 empty the corresponding member of the envelope is the empty 5089 string. 5091 Note: some servers may return a NIL envelope member in the 5092 "present but empty" case. Clients SHOULD treat NIL and 5093 empty string as identical. 5095 Note: [RFC-5322] requires that all messages have a valid 5096 Date header. Therefore, the date member in the envelope can 5097 not be NIL or the empty string. 5099 Note: [RFC-5322] requires that the In-Reply-To and Message- 5100 ID headers, if present, have non-empty content. Therefore, 5101 the in-reply-to and message-id members in the envelope can 5102 not be the empty string. 5104 If the From, To, Cc, and Bcc header lines are absent in the 5105 [RFC-5322] header, or are present but empty, the corresponding 5106 member of the envelope is NIL. 5108 If the Sender or Reply-To lines are absent in the [RFC-5322] 5109 header, or are present but empty, the server sets the 5110 corresponding member of the envelope to be the same value as 5111 the from member (the client is not expected to know to do 5112 this). 5114 Note: [RFC-5322] requires that all messages have a valid 5115 From header. Therefore, the from, sender, and reply-to 5116 members in the envelope can not be NIL. 5118 FLAGS A parenthesized list of flags that are set for this message. 5120 INTERNALDATE A string representing the internal date of the message. 5122 RFC822 Equivalent to BODY[]. 5124 RFC822.HEADER Equivalent to BODY[HEADER]. Note that this did not 5125 result in \Seen being set, because RFC822.HEADER response data 5126 occurs as a result of a FETCH of RFC822.HEADER. BODY[HEADER] 5127 response data occurs as a result of a FETCH of BODY[HEADER] (which 5128 sets \Seen) or BODY.PEEK[HEADER] (which does not set \Seen). 5130 RFC822.SIZE A number expressing the [RFC-5322] size of the message. 5132 RFC822.TEXT Equivalent to BODY[TEXT]. 5134 UID A number expressing the unique identifier of the message. 5136 Example: S: * 23 FETCH (FLAGS (\Seen) RFC822.SIZE 44827) 5138 7.5. Server Responses - Command Continuation Request 5140 The command continuation request response is indicated by a "+" token 5141 instead of a tag. This form of response indicates that the server is 5142 ready to accept the continuation of a command from the client. The 5143 remainder of this response is a line of text. 5145 This response is used in the AUTHENTICATE command to transmit server 5146 data to the client, and request additional client data. This 5147 response is also used if an argument to any command is a 5148 synchronizing literal. 5150 The client is not permitted to send the octets of the synchronizing 5151 literal unless the server indicates that it is expected. This 5152 permits the server to process commands and reject errors on a line- 5153 by-line basis. The remainder of the command, including the CRLF that 5154 terminates a command, follows the octets of the literal. If there 5155 are any additional command arguments, the literal octets are followed 5156 by a space and those arguments. 5158 Example: C: A001 LOGIN {11} 5159 S: + Ready for additional command text 5160 C: FRED FOOBAR {7} 5161 S: + Ready for additional command text 5162 C: fat man 5163 S: A001 OK LOGIN completed 5164 C: A044 BLURDYBLOOP {102856} 5165 S: A044 BAD No such command as "BLURDYBLOOP" 5167 8. Sample IMAP4rev2 connection 5169 The following is a transcript of an IMAP4rev2 connection. A long 5170 line in this sample is broken for editorial clarity. 5172 S: * OK IMAP4rev2 Service Ready 5173 C: a001 login mrc secret 5174 S: a001 OK LOGIN completed 5175 C: a002 select inbox 5176 S: * 18 EXISTS 5177 S: * FLAGS (\Answered \Flagged \Deleted \Seen \Draft) 5178 S: * OK [UIDVALIDITY 3857529045] UIDs valid 5179 S: a002 OK [READ-WRITE] SELECT completed 5180 C: a003 fetch 12 full 5181 S: * 12 FETCH (FLAGS (\Seen) INTERNALDATE "17-Jul-1996 02:44:25 -0700" 5182 RFC822.SIZE 4286 ENVELOPE ("Wed, 17 Jul 1996 02:23:25 -0700 (PDT)" 5183 "IMAP4rev2 WG mtg summary and minutes" 5184 (("Terry Gray" NIL "gray" "cac.washington.edu")) 5185 (("Terry Gray" NIL "gray" "cac.washington.edu")) 5186 (("Terry Gray" NIL "gray" "cac.washington.edu")) 5187 ((NIL NIL "imap" "cac.washington.edu")) 5188 ((NIL NIL "minutes" "CNRI.Reston.VA.US") 5189 ("John Klensin" NIL "KLENSIN" "MIT.EDU")) NIL NIL 5190 "") 5191 BODY ("TEXT" "PLAIN" ("CHARSET" "US-ASCII") NIL NIL "7BIT" 3028 5192 92)) 5193 S: a003 OK FETCH completed 5194 C: a004 fetch 12 body[header] 5195 S: * 12 FETCH (BODY[HEADER] {342} 5196 S: Date: Wed, 17 Jul 1996 02:23:25 -0700 (PDT) 5197 S: From: Terry Gray 5198 S: Subject: IMAP4rev2 WG mtg summary and minutes 5199 S: To: imap@cac.washington.edu 5200 S: cc: minutes@CNRI.Reston.VA.US, John Klensin 5201 S: Message-Id: 5202 S: MIME-Version: 1.0 5203 S: Content-Type: TEXT/PLAIN; CHARSET=US-ASCII 5204 S: 5205 S: ) 5206 S: a004 OK FETCH completed 5207 C: a005 store 12 +flags \deleted 5208 S: * 12 FETCH (FLAGS (\Seen \Deleted)) 5209 S: a005 OK +FLAGS completed 5210 C: a006 logout 5211 S: * BYE IMAP4rev2 server terminating connection 5212 S: a006 OK LOGOUT completed 5214 9. Formal Syntax 5216 The following syntax specification uses the Augmented Backus-Naur 5217 Form (ABNF) notation as specified in [ABNF]. 5219 In the case of alternative or optional rules in which a later rule 5220 overlaps an earlier rule, the rule which is listed earlier MUST take 5221 priority. For example, "\Seen" when parsed as a flag is the \Seen 5222 flag name and not a flag-extension, even though "\Seen" can be parsed 5223 as a flag-extension. Some, but not all, instances of this rule are 5224 noted below. 5226 Note: [ABNF] rules MUST be followed strictly; in particular: 5228 (1) Except as noted otherwise, all alphabetic characters are case- 5229 insensitive. The use of upper or lower case characters to define 5230 token strings is for editorial clarity only. Implementations MUST 5231 accept these strings in a case-insensitive fashion. 5233 (2) In all cases, SP refers to exactly one space. It is NOT 5234 permitted to substitute TAB, insert additional spaces, or 5235 otherwise treat SP as being equivalent to LWSP. 5237 (3) The ASCII NUL character, %x00, MUST NOT be used at any time. 5239 address = "(" addr-name SP addr-adl SP addr-mailbox SP 5240 addr-host ")" 5242 addr-adl = nstring 5243 ; Holds route from [RFC-5322] route-addr if 5244 ; non-NIL 5246 addr-host = nstring 5247 ; NIL indicates [RFC-5322] group syntax. 5248 ; Otherwise, holds [RFC-5322] domain name 5250 addr-mailbox = nstring 5251 ; NIL indicates end of [RFC-5322] group; if 5252 ; non-NIL and addr-host is NIL, holds 5253 ; [RFC-5322] group name. 5254 ; Otherwise, holds [RFC-5322] local-part 5255 ; after removing [RFC-5322] quoting 5257 addr-name = nstring 5258 ; If non-NIL, holds phrase from [RFC-5322] 5259 ; mailbox after removing [RFC-5322] quoting 5261 append = "APPEND" SP mailbox [SP flag-list] [SP date-time] SP 5262 literal 5264 append-uid = uniqueid 5266 astring = 1*ASTRING-CHAR / string 5267 ASTRING-CHAR = ATOM-CHAR / resp-specials 5269 atom = 1*ATOM-CHAR 5271 ATOM-CHAR = 5273 atom-specials = "(" / ")" / "{" / SP / CTL / list-wildcards / 5274 quoted-specials / resp-specials 5276 authenticate = "AUTHENTICATE" SP auth-type [SP initial-resp] 5277 *(CRLF base64) 5279 auth-type = atom 5280 ; Defined by [SASL] 5282 base64 = *(4base64-char) [base64-terminal] 5284 base64-char = ALPHA / DIGIT / "+" / "/" 5285 ; Case-sensitive 5287 base64-terminal = (2base64-char "==") / (3base64-char "=") 5289 body = "(" (body-type-1part / body-type-mpart) ")" 5291 body-extension = nstring / number / 5292 "(" body-extension *(SP body-extension) ")" 5293 ; Future expansion. Client implementations 5294 ; MUST accept body-extension fields. Server 5295 ; implementations MUST NOT generate 5296 ; body-extension fields except as defined by 5297 ; future standard or standards-track 5298 ; revisions of this specification. 5300 body-ext-1part = body-fld-md5 [SP body-fld-dsp [SP body-fld-lang 5301 [SP body-fld-loc *(SP body-extension)]]] 5302 ; MUST NOT be returned on non-extensible 5303 ; "BODY" fetch 5305 body-ext-mpart = body-fld-param [SP body-fld-dsp [SP body-fld-lang 5306 [SP body-fld-loc *(SP body-extension)]]] 5307 ; MUST NOT be returned on non-extensible 5308 ; "BODY" fetch 5310 body-fields = body-fld-param SP body-fld-id SP body-fld-desc SP 5311 body-fld-enc SP body-fld-octets 5313 body-fld-desc = nstring 5314 body-fld-dsp = "(" string SP body-fld-param ")" / nil 5316 body-fld-enc = (DQUOTE ("7BIT" / "8BIT" / "BINARY" / "BASE64"/ 5317 "QUOTED-PRINTABLE") DQUOTE) / string 5319 body-fld-id = nstring 5321 body-fld-lang = nstring / "(" string *(SP string) ")" 5323 body-fld-loc = nstring 5325 body-fld-lines = number 5327 body-fld-md5 = nstring 5329 body-fld-octets = number 5331 body-fld-param = "(" string SP string *(SP string SP string) ")" / nil 5333 body-type-1part = (body-type-basic / body-type-msg / body-type-text) 5334 [SP body-ext-1part] 5336 body-type-basic = media-basic SP body-fields 5337 ; MESSAGE subtype MUST NOT be "RFC822" or "GLOBAL" 5339 body-type-mpart = 1*body SP media-subtype 5340 [SP body-ext-mpart] 5341 ; MULTIPART body part 5343 body-type-msg = media-message SP body-fields SP envelope 5344 SP body SP body-fld-lines 5346 body-type-text = media-text SP body-fields SP body-fld-lines 5348 capability = ("AUTH=" auth-type) / atom 5349 ; New capabilities MUST begin with "X" or be 5350 ; registered with IANA as standard or 5351 ; standards-track 5353 capability-data = "CAPABILITY" *(SP capability) SP "IMAP4rev2" 5354 *(SP capability) 5355 ; Servers MUST implement the STARTTLS, AUTH=PLAIN, 5356 ; and LOGINDISABLED capabilities 5357 ; Servers which offer RFC 1730 compatibility MUST 5358 ; list "IMAP4" as the first capability. 5360 CHAR8 = %x01-ff 5361 ; any OCTET except NUL, %x00 5363 charset = atom / quoted 5365 command = tag SP (command-any / command-auth / command-nonauth / 5366 command-select) CRLF 5367 ; Modal based on state 5369 command-any = "CAPABILITY" / "LOGOUT" / "NOOP" / enable / x-command 5370 ; Valid in all states 5372 command-auth = append / create / delete / examine / list / lsub / 5373 Namespace-Command / 5374 rename / select / status / subscribe / unsubscribe / 5375 idle 5376 ; Valid only in Authenticated or Selected state 5378 command-nonauth = login / authenticate / "STARTTLS" 5379 ; Valid only when in Not Authenticated state 5381 command-select = "CLOSE" / "UNSELECT" / "EXPUNGE" / copy / 5382 move / fetch / store / search / uid 5383 ; Valid only when in Selected state 5385 continue-req = "+" SP (resp-text / base64) CRLF 5387 copy = "COPY" SP sequence-set SP mailbox 5389 create = "CREATE" SP mailbox 5390 ; Use of INBOX gives a NO error 5392 date = date-text / DQUOTE date-text DQUOTE 5394 date-day = 1*2DIGIT 5395 ; Day of month 5397 date-day-fixed = (SP DIGIT) / 2DIGIT 5398 ; Fixed-format version of date-day 5400 date-month = "Jan" / "Feb" / "Mar" / "Apr" / "May" / "Jun" / 5401 "Jul" / "Aug" / "Sep" / "Oct" / "Nov" / "Dec" 5403 date-text = date-day "-" date-month "-" date-year 5405 date-year = 4DIGIT 5407 date-time = DQUOTE date-day-fixed "-" date-month "-" date-year 5408 SP time SP zone DQUOTE 5410 delete = "DELETE" SP mailbox 5411 ; Use of INBOX gives a NO error 5413 digit-nz = %x31-39 5414 ; 1-9 5416 enable = "ENABLE" 1*(SP capability) 5418 enable-data = "ENABLED" *(SP capability) 5420 envelope = "(" env-date SP env-subject SP env-from SP 5421 env-sender SP env-reply-to SP env-to SP env-cc SP 5422 env-bcc SP env-in-reply-to SP env-message-id ")" 5424 env-bcc = "(" 1*address ")" / nil 5426 env-cc = "(" 1*address ")" / nil 5428 env-date = nstring 5430 env-from = "(" 1*address ")" / nil 5432 env-in-reply-to = nstring 5434 env-message-id = nstring 5436 env-reply-to = "(" 1*address ")" / nil 5438 env-sender = "(" 1*address ")" / nil 5440 env-subject = nstring 5442 env-to = "(" 1*address ")" / nil 5444 esearch-response = "ESEARCH" [search-correlator] [SP "UID"] 5445 *(SP search-return-data) 5446 ; ESEARCH response replaces SEARCH response 5447 ; from IMAP4rev1. 5449 examine = "EXAMINE" SP mailbox 5451 fetch = "FETCH" SP sequence-set SP ("ALL" / "FULL" / "FAST" / 5452 fetch-att / "(" fetch-att *(SP fetch-att) ")") 5454 fetch-att = "ENVELOPE" / "FLAGS" / "INTERNALDATE" / 5455 "RFC822" [".HEADER" / ".SIZE" / ".TEXT"] / 5456 "BODY" ["STRUCTURE"] / "UID" / 5457 "BODY" section [partial] / 5458 "BODY.PEEK" section [partial] / 5459 "BINARY" [".PEEK"] section-binary [partial] / 5460 "BINARY.SIZE" section-binary 5462 flag = "\Answered" / "\Flagged" / "\Deleted" / 5463 "\Seen" / "\Draft" / flag-keyword / flag-extension 5464 ; Does not include "\Recent" 5466 flag-extension = "\" atom 5467 ; Future expansion. Client implementations 5468 ; MUST accept flag-extension flags. Server 5469 ; implementations MUST NOT generate 5470 ; flag-extension flags except as defined by 5471 ; future standard or standards-track 5472 ; revisions of this specification. 5473 ; "\Recent" was defined in RFC 3501 5474 ; and is now deprecated. 5476 flag-fetch = flag 5478 flag-keyword = "$MDNSent" / "$Forwarded" / atom 5480 flag-list = "(" [flag *(SP flag)] ")" 5482 flag-perm = flag / "\*" 5484 greeting = "*" SP (resp-cond-auth / resp-cond-bye) CRLF 5486 header-fld-name = astring 5488 header-list = "(" header-fld-name *(SP header-fld-name) ")" 5490 idle = "IDLE" CRLF "DONE" 5492 initial-resp = (base64 / "=") 5493 ; "initial response" defined in 5494 ; Section 5.1 of [RFC4422] 5496 list = "LIST" SP mailbox SP list-mailbox 5498 list-mailbox = 1*list-char / string 5500 list-char = ATOM-CHAR / list-wildcards / resp-specials 5502 list-wildcards = "%" / "*" 5504 literal = "{" number ["+"] "}" CRLF *CHAR8 5505 ; represents the number of CHAR8s. 5506 ; A non-synchronizing literal is distinguished from 5507 ; a synchronizing literal by presence of the "+" 5508 ; before the closing "}". 5509 ; Non synchronizing literals are not allowed when 5510 ; sent from server to the client. 5512 literal8 = "~{" number "}" CRLF *OCTET 5513 ; represents the number of OCTETs 5514 ; in the response string. 5516 login = "LOGIN" SP userid SP password 5518 lsub = "LSUB" SP mailbox SP list-mailbox 5520 mailbox = "INBOX" / astring 5521 ; INBOX is case-insensitive. All case variants of 5522 ; INBOX (e.g., "iNbOx") MUST be interpreted as INBOX 5523 ; not as an astring. An astring which consists of 5524 ; the case-insensitive sequence "I" "N" "B" "O" "X" 5525 ; is considered to be INBOX and not an astring. 5526 ; Refer to section 5.1 for further 5527 ; semantic details of mailbox names. 5529 mailbox-data = "FLAGS" SP flag-list / "LIST" SP mailbox-list / 5530 "LSUB" SP mailbox-list / esearch-response / 5531 "STATUS" SP mailbox SP "(" [status-att-list] ")" / 5532 number SP "EXISTS" / Namespace-Response 5534 mailbox-list = "(" [mbx-list-flags] ")" SP 5535 (DQUOTE QUOTED-CHAR DQUOTE / nil) SP mailbox 5537 mbx-list-flags = *(mbx-list-oflag SP) mbx-list-sflag 5538 *(SP mbx-list-oflag) / 5539 mbx-list-oflag *(SP mbx-list-oflag) 5541 mbx-list-oflag = "\Noinferiors" / flag-extension 5542 ; Other flags; multiple possible per LIST response 5544 mbx-list-sflag = "\Noselect" / "\Marked" / "\Unmarked" 5545 ; Selectability flags; only one per LIST response 5547 media-basic = ((DQUOTE ("APPLICATION" / "AUDIO" / "IMAGE" / 5548 "MESSAGE" / "VIDEO" / "FONT") DQUOTE) / string) SP 5549 media-subtype 5550 ; Defined in [MIME-IMT]. 5551 ; FONT defined in RFC YYYY. 5553 media-message = DQUOTE "MESSAGE" DQUOTE SP 5554 DQUOTE ("RFC822" / "GLOBAL") DQUOTE 5555 ; Defined in [MIME-IMT] 5557 media-subtype = string 5558 ; Defined in [MIME-IMT] 5560 media-text = DQUOTE "TEXT" DQUOTE SP media-subtype 5561 ; Defined in [MIME-IMT] 5563 message-data = nz-number SP ("EXPUNGE" / ("FETCH" SP msg-att)) 5565 move = "MOVE" SP sequence-set SP mailbox 5567 msg-att = "(" (msg-att-dynamic / msg-att-static) 5568 *(SP (msg-att-dynamic / msg-att-static)) ")" 5570 msg-att-dynamic = "FLAGS" SP "(" [flag-fetch *(SP flag-fetch)] ")" 5571 ; MAY change for a message 5573 msg-att-static = "ENVELOPE" SP envelope / "INTERNALDATE" SP date-time / 5574 "RFC822" [".HEADER" / ".TEXT"] SP nstring / 5575 "RFC822.SIZE" SP number / 5576 "BODY" ["STRUCTURE"] SP body / 5577 "BODY" section ["<" number ">"] SP nstring / 5578 "BINARY" section-binary SP (nstring / literal8) / 5579 "BINARY.SIZE" section-binary SP number / 5580 "UID" SP uniqueid 5581 ; MUST NOT change for a message 5583 Namespace = nil / "(" 1*Namespace-Descr ")" 5585 Namespace-Command = "NAMESPACE" 5587 Namespace-Descr = "(" string SP 5588 (DQUOTE QUOTED-CHAR DQUOTE / nil) 5589 [Namespace-Response-Extensions] ")" 5591 Namespace-Response-Extensions = *(Namespace-Response-Extension) 5593 Namespace-Response-Extension = SP string SP 5594 "(" string *(SP string) ")" 5596 Namespace-Response = "NAMESPACE" SP Namespace 5597 SP Namespace SP Namespace 5598 ; The first Namespace is the Personal Namespace(s) 5599 ; The second Namespace is the Other Users' Namespace(s) 5600 ; The third Namespace is the Shared Namespace(s) 5602 nil = "NIL" 5603 nstring = string / nil 5605 number = 1*DIGIT 5606 ; Unsigned 32-bit integer 5607 ; (0 <= n < 4,294,967,296) 5609 number64 = 1*DIGIT 5610 ; Unsigned 63-bit integer 5611 ; (0 <= n <= 9,223,372,036,854,775,807) 5613 nz-number = digit-nz *DIGIT 5614 ; Non-zero unsigned 32-bit integer 5615 ; (0 < n < 4,294,967,296) 5617 password = astring 5619 partial-range = number ["." nz-number] 5620 ; Copied from RFC 5092 (IMAP URL) 5622 partial = "<" number "." nz-number ">" 5623 ; Partial FETCH request. 0-based offset of 5624 ; the first octet, followed by the number of octets 5625 ; in the fragment. 5627 quoted = DQUOTE *QUOTED-CHAR DQUOTE 5629 QUOTED-CHAR = / 5630 "\" quoted-specials / UTF8-2 / UTF8-3 / UTF8-4 5632 quoted-specials = DQUOTE / "\" 5634 rename = "RENAME" SP mailbox SP mailbox 5635 ; Use of INBOX as a destination gives a NO error 5637 response = *(continue-req / response-data) response-done 5639 response-data = "*" SP (resp-cond-state / resp-cond-bye / 5640 mailbox-data / message-data / capability-data / 5641 enable-data) CRLF 5643 response-done = response-tagged / response-fatal 5645 response-fatal = "*" SP resp-cond-bye CRLF 5646 ; Server closes connection immediately 5648 response-tagged = tag SP resp-cond-state CRLF 5650 resp-code-apnd = "APPENDUID" SP nz-number SP append-uid 5651 resp-code-copy = "COPYUID" SP nz-number SP uid-set SP uid-set 5653 resp-cond-auth = ("OK" / "PREAUTH") SP resp-text 5654 ; Authentication condition 5656 resp-cond-bye = "BYE" SP resp-text 5658 resp-cond-state = ("OK" / "NO" / "BAD") SP resp-text 5659 ; Status condition 5661 resp-specials = "]" 5663 ;; ////Can we make "text" optional? Will this have any bad side effects? 5664 resp-text = ["[" resp-text-code "]" SP] text 5666 resp-text-code = "ALERT" / 5667 "BADCHARSET" [SP "(" charset *(SP charset) ")" ] / 5668 capability-data / "PARSE" / 5669 "PERMANENTFLAGS" SP "(" 5670 [flag-perm *(SP flag-perm)] ")" / 5671 "READ-ONLY" / "READ-WRITE" / "TRYCREATE" / 5672 "UIDNEXT" SP nz-number / "UIDVALIDITY" SP nz-number / 5673 resp-code-apnd / resp-code-copy / "UIDNOTSTICKY" / 5674 "UNAVAILABLE" / "AUTHENTICATIONFAILED" / 5675 "AUTHORIZATIONFAILED" / "EXPIRED" / 5676 "PRIVACYREQUIRED" / "CONTACTADMIN" / "NOPERM" / 5677 "INUSE" / "EXPUNGEISSUED" / "CORRUPTION" / 5678 "SERVERBUG" / "CLIENTBUG" / "CANNOT" / 5679 "LIMIT" / "OVERQUOTA" / "ALREADYEXISTS" / 5680 "NONEXISTENT" / 5681 "CLOSED" / 5682 "UNKNOWN-CTE" / 5683 atom [SP 1*] 5685 search = "SEARCH" [search-return-opts] 5686 SP search-program 5688 search-correlator = SP "(" "TAG" SP tag-string ")" 5690 search-key = "ALL" / "ANSWERED" / "BCC" SP astring / 5691 "BEFORE" SP date / "BODY" SP astring / 5692 "CC" SP astring / "DELETED" / "FLAGGED" / 5693 "FROM" SP astring / "KEYWORD" SP flag-keyword / 5694 "NEW" / "OLD" / "ON" SP date / "SEEN" / 5695 "SINCE" SP date / "SUBJECT" SP astring / 5696 "TEXT" SP astring / "TO" SP astring / 5697 "UNANSWERED" / "UNDELETED" / "UNFLAGGED" / 5698 "UNKEYWORD" SP flag-keyword / "UNSEEN" / 5699 ; Above this line were in [IMAP2] 5700 "DRAFT" / "HEADER" SP header-fld-name SP astring / 5701 "LARGER" SP number / "NOT" SP search-key / 5702 "OR" SP search-key SP search-key / 5703 "SENTBEFORE" SP date / "SENTON" SP date / 5704 "SENTSINCE" SP date / "SMALLER" SP number / 5705 "UID" SP sequence-set / "UNDRAFT" / sequence-set / 5706 "(" search-key *(SP search-key) ")" 5708 search-modifier-name = tagged-ext-label 5710 search-mod-params = tagged-ext-val 5711 ; This non-terminal shows recommended syntax 5712 ; for future extensions. 5714 search-program = ["CHARSET" SP charset SP] 5715 search-key *(SP search-key) 5716 ; CHARSET argument to SEARCH MUST be 5717 ; registered with IANA. 5719 search-ret-data-ext = search-modifier-name SP search-return-value 5720 ; Note that not every SEARCH return option 5721 ; is required to have the corresponding 5722 ; ESEARCH return data. 5724 search-return-data = "MIN" SP nz-number / 5725 "MAX" SP nz-number / 5726 "ALL" SP sequence-set / 5727 "COUNT" SP number / 5728 search-ret-data-ext 5729 ; All return data items conform to 5730 ; search-ret-data-ext syntax 5732 search-return-opts = SP "RETURN" SP "(" [search-return-opt 5733 *(SP search-return-opt)] ")" 5735 search-return-opt = "MIN" / "MAX" / "ALL" / "COUNT" / 5736 search-ret-opt-ext 5737 ; conforms to generic search-ret-opt-ext 5738 ; syntax 5740 search-ret-opt-ext = search-modifier-name [SP search-mod-params] 5742 search-return-value = tagged-ext-val 5743 ; Data for the returned search option. 5744 ; A single "nz-number"/"number"/"number64" value 5745 ; can be returned as an atom (i.e., without 5746 ; quoting). A sequence-set can be returned 5747 ; as an atom as well. 5749 section = "[" [section-spec] "]" 5751 section-binary = "[" [section-part] "]" 5753 section-msgtext = "HEADER" / "HEADER.FIELDS" [".NOT"] SP header-list / 5754 "TEXT" 5755 ; top-level or MESSAGE/RFC822 or MESSAGE/GLOBAL part 5757 section-part = nz-number *("." nz-number) 5758 ; body part reference. 5759 ; Allows for accessing nested body parts. 5761 section-spec = section-msgtext / (section-part ["." section-text]) 5763 section-text = section-msgtext / "MIME" 5764 ; text other than actual body part (headers, etc.) 5766 select = "SELECT" SP mailbox 5768 seq-number = nz-number / "*" 5769 ; message sequence number (COPY, FETCH, STORE 5770 ; commands) or unique identifier (UID COPY, 5771 ; UID FETCH, UID STORE commands). 5772 ; * represents the largest number in use. In 5773 ; the case of message sequence numbers, it is 5774 ; the number of messages in a non-empty mailbox. 5775 ; In the case of unique identifiers, it is the 5776 ; unique identifier of the last message in the 5777 ; mailbox or, if the mailbox is empty, the 5778 ; mailbox's current UIDNEXT value. 5779 ; The server should respond with a tagged BAD 5780 ; response to a command that uses a message 5781 ; sequence number greater than the number of 5782 ; messages in the selected mailbox. This 5783 ; includes "*" if the selected mailbox is empty. 5785 seq-range = seq-number ":" seq-number 5786 ; two seq-number values and all values between 5787 ; these two regardless of order. 5788 ; Example: 2:4 and 4:2 are equivalent and indicate 5789 ; values 2, 3, and 4. 5790 ; Example: a unique identifier sequence range of 5791 ; 3291:* includes the UID of the last message in 5792 ; the mailbox, even if that value is less than 3291. 5794 sequence-set = (seq-number / seq-range) ["," sequence-set] 5795 ; set of seq-number values, regardless of order. 5796 ; Servers MAY coalesce overlaps and/or execute the 5797 ; sequence in any order. 5798 ; Example: a message sequence number set of 5799 ; 2,4:7,9,12:* for a mailbox with 15 messages is 5800 ; equivalent to 2,4,5,6,7,9,12,13,14,15 5801 ; Example: a message sequence number set of *:4,5:7 5802 ; for a mailbox with 10 messages is equivalent to 5803 ; 10,9,8,7,6,5,4,5,6,7 and MAY be reordered and 5804 ; overlap coalesced to be 4,5,6,7,8,9,10. 5806 status = "STATUS" SP mailbox SP 5807 "(" status-att *(SP status-att) ")" 5809 status-att = "MESSAGES" / "UIDNEXT" / "UIDVALIDITY" / 5810 "UNSEEN" / "SIZE" 5812 status-att-val = ("MESSAGES" SP number) / 5813 ("UIDNEXT" SP nz-number) / 5814 ("UIDVALIDITY" SP nz-number) / 5815 ("UNSEEN" SP number) / 5816 ("SIZE" SP number64) 5817 ; Extensions to the STATUS responses 5818 ; should extend this production. 5819 ; Extensions should use the generic 5820 ; syntax defined by tagged-ext. 5822 status-att-list = status-att-val *(SP status-att-val) 5824 store = "STORE" SP sequence-set SP store-att-flags 5826 store-att-flags = (["+" / "-"] "FLAGS" [".SILENT"]) SP 5827 (flag-list / (flag *(SP flag))) 5829 string = quoted / literal 5831 subscribe = "SUBSCRIBE" SP mailbox 5833 tag = 1* 5835 tagged-ext-label = tagged-label-fchar *tagged-label-char 5836 ;; Is a valid RFC 3501 "atom". 5838 tagged-label-fchar = ALPHA / "-" / "_" / "." 5840 tagged-label-char = tagged-label-fchar / DIGIT / ":" 5842 tagged-ext-comp = astring / 5843 tagged-ext-comp *(SP tagged-ext-comp) / 5844 "(" tagged-ext-comp ")" 5845 ;; Extensions that follow this general 5846 ;; syntax should use nstring instead of 5847 ;; astring when appropriate in the context 5848 ;; of the extension. 5849 ;; Note that a message set or a "number" 5850 ;; can always be represented as an "atom". 5851 ;; An URL should be represented as 5852 ;; a "quoted" string. 5854 tagged-ext-simple = sequence-set / number / number64 5856 tagged-ext-val = tagged-ext-simple / 5857 "(" [tagged-ext-comp] ")" 5859 text = 1*TEXT-CHAR 5861 TEXT-CHAR = 5863 time = 2DIGIT ":" 2DIGIT ":" 2DIGIT 5864 ; Hours minutes seconds 5866 uid = "UID" SP 5867 (copy / move / fetch / search / store / uid-expunge) 5868 ; Unique identifiers used instead of message 5869 ; sequence numbers 5871 uid-expunge = "EXPUNGE" SP sequence-set 5872 ; Unique identifiers used instead of message 5873 ; sequence numbers 5875 uid-set = (uniqueid / uid-range) *("," uid-set) 5877 uid-range = (uniqueid ":" uniqueid) 5878 ; two uniqueid values and all values 5879 ; between these two regards of order. 5880 ; Example: 2:4 and 4:2 are equivalent. 5882 uniqueid = nz-number 5883 ; Strictly ascending 5885 unsubscribe = "UNSUBSCRIBE" SP mailbox 5887 userid = astring 5889 UTF8-2 = 5890 UTF8-3 = 5892 UTF8-4 = 5894 x-command = "X" atom 5896 zone = ("+" / "-") 4DIGIT 5897 ; Signed four-digit value of hhmm representing 5898 ; hours and minutes east of Greenwich (that is, 5899 ; the amount that the given time differs from 5900 ; Universal Time). Subtracting the timezone 5901 ; from the given time will give the UT form. 5902 ; The Universal Time zone is "+0000". 5904 10. Author's Note 5906 This document is a revision or rewrite of earlier documents, and 5907 supercedes the protocol specification in those documents: RFC 2060, 5908 RFC 1730, unpublished IMAP2bis.TXT document, RFC 1176, and RFC 1064. 5910 11. Security Considerations 5912 IMAP4rev2 protocol transactions, including electronic mail data, are 5913 sent in the clear over the network unless protection from snooping is 5914 negotiated. This can be accomplished either by the use of IMAPS 5915 service, STARTTLS command, negotiated privacy protection in the 5916 AUTHENTICATE command, or some other protection mechanism. 5918 11.1. STARTTLS Security Considerations 5920 IMAP client and server implementations MUST comply with relevant TLS 5921 recommendations from [RFC8314]. Additionally, when using TLS 1.2, 5922 IMAP implementations MUST implement 5923 TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256 cipher suite, and SHOULD 5924 implement the TLS_RSA_WITH_AES_128_CBC_SHA [TLS] cipher suite. This 5925 is important as it assures that any two compliant implementations can 5926 be configured to interoperate. Other TLS cipher suites recommended 5927 in RFC 7525 are RECOMMENDED: TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256, 5928 TLS_DHE_RSA_WITH_AES_256_GCM_SHA384 and 5929 TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384. All other cipher suites are 5930 OPTIONAL. Note that this is a change from section 2.1 of [IMAP-TLS]. 5932 During the [TLS] negotiation, the client MUST check its understanding 5933 of the server hostname against the server's identity as presented in 5934 the server Certificate message, in order to prevent man-in-the-middle 5935 attacks. This procedure is described in [RFC7817]. 5937 Both the client and server MUST check the result of the STARTTLS 5938 command and subsequent [TLS] negotiation to see whether acceptable 5939 authentication and/or privacy was achieved. 5941 11.2. COPYUID and APPENDUID response codes 5943 The COPYUID and APPENDUID response codes return information about the 5944 mailbox, which may be considered sensitive if the mailbox has 5945 permissions set that permit the client to COPY or APPEND to the 5946 mailbox, but not SELECT or EXAMINE it. 5948 Consequently, these response codes SHOULD NOT be issued if the client 5949 does not have access to SELECT or EXAMINE the mailbox. 5951 11.3. LIST command and Other Users' namespace 5953 In response to a LIST command containing an argument of the Other 5954 Users' Namespace prefix, a server SHOULD NOT list users that have not 5955 granted list access to their personal mailboxes to the currently 5956 authenticated user. Providing such a list, could compromise security 5957 by potentially disclosing confidential information of who is located 5958 on the server, or providing a starting point of a list of user 5959 accounts to attack. 5961 11.4. Other Security Considerations 5963 A server error message for an AUTHENTICATE command which fails due to 5964 invalid credentials SHOULD NOT detail why the credentials are 5965 invalid. 5967 Use of the LOGIN command sends passwords in the clear. This can be 5968 avoided by using the AUTHENTICATE command with a [SASL] mechanism 5969 that does not use plaintext passwords, by first negotiating 5970 encryption via STARTTLS or some other protection mechanism. 5972 A server implementation MUST implement a configuration that, at the 5973 time of authentication, requires: 5974 (1) The STARTTLS command has been negotiated. 5975 OR 5976 (2) Some other mechanism that protects the session from password 5977 snooping has been provided. 5978 OR 5979 (3) The following measures are in place: 5980 (a) The LOGINDISABLED capability is advertised, and [SASL] mechanisms 5981 (such as PLAIN) using plaintext passwords are NOT advertised in the 5982 CAPABILITY list. 5983 AND 5984 (b) The LOGIN command returns an error even if the password is 5985 correct. 5986 AND 5987 (c) The AUTHENTICATE command returns an error with all [SASL] 5988 mechanisms that use plaintext passwords, even if the password is 5989 correct. 5991 A server error message for a failing LOGIN command SHOULD NOT specify 5992 that the user name, as opposed to the password, is invalid. 5994 A server SHOULD have mechanisms in place to limit or delay failed 5995 AUTHENTICATE/LOGIN attempts. 5997 Additional security considerations are discussed in the section 5998 discussing the AUTHENTICATE and LOGIN commands. 6000 12. IANA Considerations 6002 IANA is requested to update "Service Names and Transport Protocol 6003 Port Numbers" registry as follows: 6005 1. Registration for TCP "imap" port 143 should be updated to point 6006 to this document and RFC 3501. 6008 2. Registration for TCP "imaps" port 993 should be updated to point 6009 to this document, RFC 8314 and RFC 3501. 6011 3. Both UDP port 143 and UDP port 993 should be marked as "Reserved" 6012 in the registry. 6014 Additional IANA actions are specified in subsection of this section. 6016 12.1. Updates to IMAP4 Capabilities registry 6018 IMAP4 capabilities are registered by publishing a standards track or 6019 IESG approved informational or experimental RFC. The registry is 6020 currently located at: http://www.iana.org/assignments/ 6021 imap4-capabilities 6023 As this specification revises the STARTTLS and LOGINDISABLED 6024 extensions previously defined in [IMAP-TLS], IANA is requested to 6025 update registry entries for these 2 extensions to point to this 6026 document. 6028 12.2. GSSAPI/SASL service name 6030 GSSAPI/Kerberos/SASL service names are registered by publishing a 6031 standards track or IESG approved experimental RFC. The registry is 6032 currently located at: http://www.iana.org/assignments/gssapi-service- 6033 names 6035 IANA is requested to update the "imap" service name previously 6036 registered in RFC 3501, to point to this document. 6038 13. References 6040 13.1. Normative References 6042 [ABNF] Crocker, D., Ed. and P. Overell, "Augmented BNF for Syntax 6043 Specifications: ABNF", STD 68, RFC 5234, January 2008, 6044 . 6046 [ANONYMOUS] 6047 Zeilenga, K., "Anonymous Simple Authentication and 6048 Security Layer (SASL) Mechanism", RFC 4505, June 2006, 6049 . 6051 [CHARSET] Freed, N. and J. Postel, "IANA Charset Registration 6052 Procedures", BCP 19, RFC 2978, October 2000, 6053 . 6055 [SCRAM-SHA-256] 6056 Hansen, T., "SCRAM-SHA-256 and SCRAM-SHA-256-PLUS Simple 6057 Authentication and Security Layer (SASL) Mechanisms", 6058 RFC 7677, DOI 10.17487/RFC7677, November 2015, 6059 . 6061 [DISPOSITION] 6062 Troost, R., Dorner, S., and K. Moore, Ed., "Communicating 6063 Presentation Information in Internet Messages: The 6064 Content-Disposition Header Field", RFC 2183, August 1997, 6065 . 6067 [PLAIN] Zeilenga, K., Ed., "The PLAIN Simple Authentication and 6068 Security Layer (SASL) Mechanism", RFC 4616, August 2006, 6069 . 6071 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 6072 Requirement Levels", BCP 14, RFC 2119, 6073 DOI 10.17487/RFC2119, March 1997, 6074 . 6076 [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 6077 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, 6078 May 2017, . 6080 [LANGUAGE-TAGS] 6081 Alvestrand, H., "Content Language Headers", RFC 3282, May 6082 2002, . 6084 [LOCATION] 6085 Palme, J., Hopmann, A., and N. Shelness, "MIME 6086 Encapsulation of Aggregate Documents, such as HTML 6087 (MHTML)", RFC 2557, March 1999, 6088 . 6090 [MD5] Myers, J. and M. Rose, "The Content-MD5 Header Field", 6091 RFC 1864, October 1995, 6092 . 6094 [MIME-HDRS] 6095 Moore, K., "MIME (Multipurpose Internet Mail Extensions) 6096 Part Three: Message Header Extensions for Non-ASCII Text", 6097 RFC 2047, November 1996, 6098 . 6100 [MIME-IMB] 6101 Freed, N. and N. Borenstein, "Multipurpose Internet Mail 6102 Extensions (MIME) Part One: Format of Internet Message 6103 Bodies", RFC 2045, November 1996, 6104 . 6106 [MIME-IMT] 6107 Freed, N. and N. Borenstein, "Multipurpose Internet Mail 6108 Extensions (MIME) Part Two: Media Types", RFC 2046, 6109 November 1996, . 6111 [RFC2231] Freed, N. and K. Moore, "MIME Parameter Value and Encoded 6112 Word Extensions: Character Sets, Languages, and 6113 Continuations", RFC 2231, DOI 10.17487/RFC2231, November 6114 1997, . 6116 [RFC-5322] 6117 Resnick, P., Ed., "Internet Message Format", RFC 5322, 6118 October 2008, . 6120 [SASL] Melnikov, A., Ed. and K. Zeilenga, Ed., "Simple 6121 Authentication and Security Layer (SASL)", RFC 4422, June 6122 2006, . 6124 [TLS] Dierks, T. and E. Rescorla, "The Transport Layer Security 6125 (TLS) Protocol Version 1.2", RFC 5246, August 2008, 6126 . 6128 [UTF-7] Goldsmith, D. and M. Davis, "UTF-7 A Mail-Safe 6129 Transformation Format of Unicode", RFC 2152, May 1997, 6130 . 6132 [UTF-8] Yergeau, F., "UTF-8, a transformation format of ISO 6133 10646", STD 63, RFC 3629, DOI 10.17487/RFC3629, November 6134 2003, . 6136 [MULTIAPPEND] 6137 Crispin, M., "Internet Message Access Protocol (IMAP) - 6138 MULTIAPPEND Extension", RFC 3502, March 2003, 6139 . 6141 [NET-UNICODE] 6142 Klensin, J. and M. Padlipsky, "Unicode Format for Network 6143 Interchange", RFC 5198, DOI 10.17487/RFC5198, March 2008, 6144 . 6146 [I18N-HDRS] 6147 Yang, A., Steele, S., and N. Freed, "Internationalized 6148 Email Headers", RFC 6532, DOI 10.17487/RFC6532, February 6149 2012, . 6151 [RFC4648] Josefsson, S., "The Base16, Base32, and Base64 Data 6152 Encodings", RFC 4648, DOI 10.17487/RFC4648, October 2006, 6153 . 6155 [RFC7817] Melnikov, A., "Updated Transport Layer Security (TLS) 6156 Server Identity Check Procedure for Email-Related 6157 Protocols", RFC 7817, DOI 10.17487/RFC7817, March 2016, 6158 . 6160 [RFC8098] Hansen, T., Ed. and A. Melnikov, Ed., "Message Disposition 6161 Notification", STD 85, RFC 8098, DOI 10.17487/RFC8098, 6162 February 2017, . 6164 [RFC8314] Moore, K. and C. Newman, "Cleartext Considered Obsolete: 6165 Use of Transport Layer Security (TLS) for Email Submission 6166 and Access", RFC 8314, DOI 10.17487/RFC8314, January 2018, 6167 . 6169 [IMAP-IMPLEMENTATION] 6170 Leiba, B., "IMAP4 Implementation Recommendations", 6171 RFC 2683, September 1999, 6172 . 6174 [IMAP-MULTIACCESS] 6175 Gahrns, M., "IMAP4 Multi-Accessed Mailbox Practice", 6176 RFC 2180, July 1997, 6177 . 6179 13.2. Informative References (related protocols) 6181 [RFC5258] Leiba, B. and A. Melnikov, "Internet Message Access 6182 Protocol version 4 - LIST Command Extensions", RFC 5258, 6183 DOI 10.17487/RFC5258, June 2008, 6184 . 6186 [RFC2193] Gahrns, M., "IMAP4 Mailbox Referrals", RFC 2193, 6187 DOI 10.17487/RFC2193, September 1997, 6188 . 6190 [RFC3348] Gahrns, M. and R. Cheng, "The Internet Message Action 6191 Protocol (IMAP4) Child Mailbox Extension", RFC 3348, 6192 DOI 10.17487/RFC3348, July 2002, 6193 . 6195 [RFC7888] Melnikov, A., Ed., "IMAP4 Non-synchronizing Literals", 6196 RFC 7888, DOI 10.17487/RFC7888, May 2016, 6197 . 6199 [IMAP-DISC] 6200 Melnikov, A., Ed., "Synchronization Operations for 6201 Disconnected IMAP4 Clients", RFC 4549, June 2006, 6202 . 6204 [IMAP-I18N] 6205 Newman, C., Gulbrandsen, A., and A. Melnikov, "Internet 6206 Message Access Protocol Internationalization", RFC 5255, 6207 DOI 10.17487/RFC5255, June 2008, 6208 . 6210 [IMAP-MODEL] 6211 Crispin, M., "Distributed Electronic Mail Models in 6212 IMAP4", RFC 1733, December 1994, 6213 . 6215 [IMAP-UTF-8] 6216 Resnick, P., Ed., Newman, C., Ed., and S. Shen, Ed., "IMAP 6217 Support for UTF-8", RFC 6855, DOI 10.17487/RFC6855, March 6218 2013, . 6220 [SMTP] Klensin, J., "Simple Mail Transfer Protocol", RFC 5321, 6221 October 2008, . 6223 [RFC3516] Nerenberg, L., "IMAP4 Binary Content Extension", RFC 3516, 6224 DOI 10.17487/RFC3516, April 2003, 6225 . 6227 [RFC4314] Melnikov, A., "IMAP4 Access Control List (ACL) Extension", 6228 RFC 4314, December 2005, 6229 . 6231 [RFC2087] Myers, J., "IMAP4 QUOTA extension", RFC 2087, January 6232 1997, . 6234 [IMAP-URL] 6235 Melnikov, A., Ed. and C. Newman, "IMAP URL Scheme", 6236 RFC 5092, DOI 10.17487/RFC5092, November 2007, 6237 . 6239 13.3. Informative References (historical aspects of IMAP and related 6240 protocols) 6242 [IMAP-COMPAT] 6243 Crispin, M., "IMAP4 Compatibility with IMAP2bis", 6244 RFC 2061, December 1996, 6245 . 6247 [IMAP-HISTORICAL] 6248 Crispin, M., "IMAP4 Compatibility with IMAP2 and 6249 IMAP2bis", RFC 1732, December 1994, 6250 . 6252 [IMAP-OBSOLETE] 6253 Crispin, M., "Internet Message Access Protocol - Obsolete 6254 Syntax", RFC 2062, December 1996, 6255 . 6257 [IMAP2] Crispin, M., "Interactive Mail Access Protocol: Version 6258 2", RFC 1176, August 1990, 6259 . 6261 [RFC-822] Crocker, D., "STANDARD FOR THE FORMAT OF ARPA INTERNET 6262 TEXT MESSAGES", STD 11, RFC 822, August 1982, 6263 . 6265 [RFC-821] Postel, J., "Simple Mail Transfer Protocol", STD 10, 6266 RFC 821, August 1982, 6267 . 6269 [IMAP-TLS] 6270 Newman, C., "Using TLS with IMAP, POP3 and ACAP", 6271 RFC 2595, June 1999, 6272 . 6274 Appendix A. Backward compatibility with IMAP4rev1 6276 An implementation that wants to remain compatible with IMAP4rev1 can 6277 advertise both IMAP4rev1 and IMAP4rev2 in its CAPABILITY response/ 6278 response code. While some IMAP4rev1 responses were removed in 6279 IMAP4rev2, their presence will not break IMAP4rev2-only clients. 6281 If both IMAP4rev1 and IMAP4rev2 are advertised, an IMAP client that 6282 wants to use IMAP4rev2 MUST issue an "ENABLE IMAP4rev2" command. 6284 Servers advertising both IMAP4rev1 and IMAP4rev2 SHOULD NOT generate 6285 UTF-8 quoted strings unless the client has issued "ENABLE IMAP4rev2". 6286 Consider implementation of mechanisms described or referenced in 6287 [IMAP-UTF-8] to achieve this goal. 6289 Servers advertising both IMAP4rev1 and IMAP4rev2, and clients 6290 intending to be compatible with IMAP4rev1 servers MUST be compatible 6291 with the international mailbox naming convention described in the 6292 following subsection. 6294 A.1. Mailbox International Naming Convention 6296 By convention, international mailbox names in IMAP4rev2 are specified 6297 using a modified version of the UTF-7 encoding described in [UTF-7]. 6298 Modified UTF-7 may also be usable in servers that implement an 6299 earlier version of this protocol. 6301 In modified UTF-7, printable US-ASCII characters, except for "&", 6302 represent themselves; that is, characters with octet values 0x20-0x25 6303 and 0x27-0x7e. The character "&" (0x26) is represented by the two- 6304 octet sequence "&-". 6306 All other characters (octet values 0x00-0x1f and 0x7f-0xff) are 6307 represented in modified BASE64, with a further modification from 6308 [UTF-7] that "," is used instead of "/". Modified BASE64 MUST NOT be 6309 used to represent any printing US-ASCII character which can represent 6310 itself. Only characters inside the modified BASE64 alphabet are 6311 permitted in modified BASE64 text. 6313 "&" is used to shift to modified BASE64 and "-" to shift back to US- 6314 ASCII. There is no implicit shift from BASE64 to US-ASCII, and null 6315 shifts ("-&" while in BASE64; note that "&-" while in US-ASCII means 6316 "&") are not permitted. However, all names start in US-ASCII, and 6317 MUST end in US-ASCII; that is, a name that ends with a non-ASCII 6318 ISO-10646 character MUST end with a "-"). 6320 The purpose of these modifications is to correct the following 6321 problems with UTF-7: 6323 1. UTF-7 uses the "+" character for shifting; this conflicts with 6324 the common use of "+" in mailbox names, in particular USENET 6325 newsgroup names. 6327 2. UTF-7's encoding is BASE64 which uses the "/" character; this 6328 conflicts with the use of "/" as a popular hierarchy delimiter. 6330 3. UTF-7 prohibits the unencoded usage of "\"; this conflicts with 6331 the use of "\" as a popular hierarchy delimiter. 6333 4. UTF-7 prohibits the unencoded usage of "~"; this conflicts with 6334 the use of "~" in some servers as a home directory indicator. 6336 5. UTF-7 permits multiple alternate forms to represent the same 6337 string; in particular, printable US-ASCII characters can be 6338 represented in encoded form. 6340 Although modified UTF-7 is a convention, it establishes certain 6341 requirements on server handling of any mailbox name with an embedded 6342 "&" character. In particular, server implementations MUST preserve 6343 the exact form of the modified BASE64 portion of a modified UTF-7 6344 name and treat that text as case-sensitive, even if names are 6345 otherwise case-insensitive or case-folded. 6347 Server implementations SHOULD verify that any mailbox name with an 6348 embedded "&" character, used as an argument to CREATE, is: in the 6349 correctly modified UTF-7 syntax, has no superfluous shifts, and has 6350 no encoding in modified BASE64 of any printing US-ASCII character 6351 which can represent itself. However, client implementations MUST NOT 6352 depend upon the server doing this, and SHOULD NOT attempt to create a 6353 mailbox name with an embedded "&" character unless it complies with 6354 the modified UTF-7 syntax. 6356 Server implementations which export a mail store that does not follow 6357 the modified UTF-7 convention MUST convert to modified UTF-7 any 6358 mailbox name that contains either non-ASCII characters or the "&" 6359 character. 6361 For example, here is a mailbox name which mixes English, Chinese, 6362 and Japanese text: ~peter/mail/&U,BTFw-/&ZeVnLIqe- 6364 For example, the string "&Jjo!" is not a valid mailbox name 6365 because it does not contain a shift to US-ASCII before the "!". 6366 The correct form is "&Jjo-!". The string "&U,BTFw-&ZeVnLIqe-" is 6367 not permitted because it contains a superfluous shift. The 6368 correct form is "&U,BTF2XlZyyKng-". 6370 Appendix B. Backward compatibility with BINARY extension 6372 IMAP4rev2 is incorporates subset of functionality provided by the 6373 BINARY extension [RFC3516], in particular it includes additional 6374 FETCH items (BINARY, BINARY.PEEK and BINARY.SIZE), but not extensions 6375 to the APPEND command. IMAP4rev2 implementations that supports full 6376 RFC 3516 functionality need to also advertise the BINARY token in the 6377 CAPABILITY response. 6379 Appendix C. Changes from RFC 3501 / IMAP4rev1 6381 The following is the plan for remaining changes. The plan might 6382 change over time. 6384 1. Fold in the following extensions/RFC: RFC 5530 (IMAP Response 6385 Codes, done), UIDPLUS (done), ENABLE (done), ESEARCH (done), 6386 SPECIAL-USE (list of new mailbox attributes is done), LITERAL- 6387 (done), NAMESPACE (done), SASL-IR (done), IDLE (done), MOVE 6388 (done). 6390 2. Add CLOSED response code (from CONDSTORE) - done 6392 3. Add support for $MDNSent and $Forwarded IMAP keywords - done. 6393 Add more examples showing their use? Also add other keywords 6394 like $Phishing, $Junk, $NonJunk? 6396 4. Require all unsolicited FETCH updates to include UID - done. 6398 5. Update recommendations on TLS ciphers to match UTA WG work (as 6399 per RFC 8314, RFC 7525 and RFC 7817) - done. 6401 6. Possibly fold in the following extensions/RFC: Base LIST- 6402 EXTENDED syntax plus deprecate LSUB (replace it with LIST 6403 \Subscribed) minus the requirement to support multiple list 6404 patterns, STATUS-in-LIST, SEARCHRES, BINARY (only the FETCH 6405 changes on leaf body part and make APPEND related ones optional. 6406 See the mailing list discussion) - done. 6408 7. Add STATUS SIZE (total mailbox size) - done Add STATUS DELETED 6409 (number of messages with \Deleted flag set)? Or DELETEDSIZE? 6411 8. Deprecate features: What should we do with NEW search key (which 6412 implies RECENT): deprecate it or just redefine it to ignore 6413 RECENT state? 6415 9. Drop UTF-7, all mailboxes are always in UTF-8 - done. 6417 10. Revise IANA registration of IMAP extensions and give advice on 6418 use of "X-" convention. 6420 11. Allow word-based searching (as per Chris Newman)? 6422 The following changes since RFC 3501 were done so far: 6424 1. Folded in IMAP UNSELECT (RFC 3691), UIDPLUS (RFC 4315), ESEARCH 6425 (RFC 4731), ENABLE (RFC 5161), IDLE (RFC 2177), SASL-IR (RFC 6426 4959) and MOVE (RFC 6851) extensions. Also folded RFC 5530 and 6427 FETCH side of the BINARY extension (RFC 3516). 6429 2. Clarified that server should decode parameter value 6430 continuations as described in [RFC2231]. This requirement was 6431 hidden in RFC 2231 itself. 6433 3. SEARCH command now requires to return ESEARCH response (SEARCH 6434 response is now deprecated). 6436 4. Added CLOSED response code from RFC 7162. 6438 5. Updated to use modern TLS-related recommendations as per RFC 6439 8314, RFC 7817, RFC 7525. 6441 6. For future extensibility extended ABNF for tagged-ext-simple to 6442 allow for bare number64. 6444 7. Added SHOULD level requirement on IMAP servers to support 6445 $MDNSent and $Forwarded keywords. 6447 8. Added STATUS SIZE. 6449 9. Mailbox names and message headers now allow for UTF-8. Support 6450 for Modified UTF-7 in mailbox names is not required, unless 6451 compatibility with IMAP4rev1 is desired. 6453 10. UNSEEN response code on SELECT/EXAMINE is now deprecated. 6455 11. RECENT response on SELECT/EXAMINE, \Recent flag, RECENT STATUS 6456 item are now deprecated. 6458 12. Clarified that the server doesn't need to send a new 6459 PERMANENTFLAGS response code when a new keyword was successfully 6460 added and the server advertised \* earlier for the same mailbox. 6462 13. Removed the CHECK command. Clients should use NOOP instead. 6464 14. Replaced DIGEST-MD5 SASL mechanism with SCRAM-SHA-256. DIGEST- 6465 MD5 was deprecated. 6467 Appendix D. Acknowledgement 6469 Earlier versions of this document were edited by Mark Crispin. 6470 Sadly, he is no longer available to help with this work. Editors of 6471 this revisions are hoping that Mark would have approved. 6473 Chris Newman has contributed text on I18N and use of UTF-8 in 6474 messages and mailbox names. 6476 Thank you to Tony Hansen for helping with the index generation. 6477 Thank you to Timo Sirainen for extensive feedback. 6479 This document incorporate text from RFC 4315, RFC 4466, RFC 4731, RFC 6480 5161, RFC 6154 so work done by authors/editors of these documents is 6481 appreciated. 6483 Index 6485 $ 6486 $Forwarded (predefined flag) 12 6487 $MDNSent (predefined flag) 12 6489 + 6490 +FLAGS 81 6491 +FLAGS.SILENT 81 6493 - 6494 -FLAGS 82 6495 -FLAGS.SILENT 82 6497 A 6498 ALERT (response code) 89 6499 ALL (fetch item) 77 6500 ALL (search key) 73 6501 ALL (search result option) 72 6502 ALREADYEXISTS (response code) 89 6503 ANSWERED (search key) 73 6504 APPEND (command) 65 6505 APPENDUID (response code) 89 6506 AUTHENTICATE (command) 28 6507 AUTHENTICATIONFAILED (response code) 90 6508 AUTHORIZATIONFAILED (response code) 90 6510 B 6511 BAD (response) 97 6512 BADCHARSET (response code) 90 6513 BCC (search key) 73 6514 BEFORE (search key) 73 6515 BINARY.PEEK[]<> (fetch item) 78 6516 BINARY.SIZE[] (fetch item) 78 6517 BINARY.SIZE[] (fetch result) 106 6518 BINARY[]<> (fetch result) 105 6519 BINARY[]<> (fetch item) 77 6520 BODY (fetch item) 78 6521 BODY (fetch result) 106 6522 BODY (search key) 74 6523 BODY.PEEK[
]<> (fetch item) 80 6524 BODYSTRUCTURE (fetch item) 80 6525 BODYSTRUCTURE (fetch result) 107 6526 BODY[
]<> (fetch result) 106 6527 BODY[
]<> (fetch item) 78 6528 BYE (response) 97 6529 Body Structure (message attribute) 13 6531 C 6532 CANNOT (response code) 90 6533 CAPABILITY (command) 24 6534 CAPABILITY (response code) 90 6535 CAPABILITY (response) 98 6536 CC (search key) 74 6537 CLIENTBUG (response code) 91 6538 CLOSE (command) 69 6539 CLOSED (response code) 91 6540 CONTACTADMIN (response code) 91 6541 COPY (command) 82 6542 COPYUID (response code) 91 6543 CORRUPTION (response code) 92 6544 COUNT (search result option) 72 6545 CREATE (command) 36 6547 D 6548 DELETE (command) 37 6549 DELETED (search key) 74 6550 DRAFT (search key) 74 6552 E 6553 ENABLE (command) 32 6554 ENVELOPE (fetch item) 80 6555 ENVELOPE (fetch result) 109 6556 ESEARCH (response) 103 6557 EXAMINE (command) 35 6558 EXPIRED (response code) 92 6559 EXPUNGE (command) 70 6560 EXPUNGE (response) 104 6561 EXPUNGEISSUED (response code) 92 6562 Envelope Structure (message attribute) 13 6564 F 6565 FAST (fetch item) 77 6566 FETCH (command) 77 6567 FETCH (response) 105 6568 FLAGGED (search key) 74 6569 FLAGS (fetch item) 80 6570 FLAGS (fetch result) 111 6571 FLAGS (response) 104 6572 FLAGS (store command data item) 81 6573 FLAGS.SILENT (store command data item) 81 6574 FROM (search key) 74 6575 FULL (fetch item) 77 6576 Flags (message attribute) 11 6578 H 6579 HEADER (part specifier) 78 6580 HEADER (search key) 74 6581 HEADER.FIELDS (part specifier) 78 6582 HEADER.FIELDS.NOT (part specifier) 78 6584 I 6585 IDLE (command) 67 6586 INTERNALDATE (fetch item) 80 6587 INTERNALDATE (fetch result) 111 6588 INUSE (response code) 92 6589 Internal Date (message attribute) 12 6591 K 6592 KEYWORD (search key) 74 6593 Keyword (type of flag) 12 6595 L 6596 LARGER (search key) 74 6597 LIMIT (response code) 93 6598 LIST (command) 41 6599 LIST (response) 99 6600 LOGOUT (command) 26 6601 LSUB (command) 58 6602 LSUB (response) 102 6604 M 6605 MAX (search result option) 72 6606 MAY (specification requirement term) 5 6607 MESSAGES (status item) 64 6608 MIME (part specifier) 79 6609 MIN (search result option) 72 6610 MOVE (command) 83 6611 MUST (specification requirement term) 5 6612 MUST NOT (specification requirement term) 5 6613 Message Sequence Number (message attribute) 11 6615 N 6616 NAMESPACE (command) 59 6617 NAMESPACE (response) 102 6618 NEW (search key) 74 6619 NO (response) 96 6620 NONEXISTENT (response code) 93 6621 NOOP (command) 25 6622 NOPERM (response code) 93 6623 NOT (search key) 74 6624 NOT RECOMMENDED (specification requirement term) 5 6626 O 6627 OK (response) 96 6628 ON (search key) 74 6629 OPTIONAL (specification requirement term) 5 6630 OR (search key) 74 6631 OVERQUOTA (response code) 93 6633 P 6634 PARSE (response code) 94 6635 PERMANENTFLAGS (response code) 94 6636 PREAUTH (response) 97 6637 PRIVACYREQUIRED (response code) 94 6638 Permanent Flag (class of flag) 12 6639 Predefined keywords 12 6641 R 6642 READ-ONLY (response code) 94 6643 READ-WRITE (response code) 94 6644 RECOMMENDED (specification requirement term) 5 6645 RENAME (command) 38 6646 REQUIRED (specification requirement term) 5 6647 RFC822 (fetch item) 80 6648 RFC822 (fetch result) 111 6649 RFC822.HEADER (fetch item) 80 6650 RFC822.HEADER (fetch result) 111 6651 RFC822.SIZE (fetch item) 80 6652 RFC822.SIZE (fetch result) 111 6653 RFC822.TEXT (fetch item) 80 6654 RFC822.TEXT (fetch result) 111 6656 S 6657 SEARCH (command) 71 6658 SEEN (search key) 74 6659 SELECT (command) 34 6660 SENTBEFORE (search key) 74 6661 SENTON (search key) 74 6662 SENTSINCE (search key) 75 6663 SERVERBUG (response code) 94 6664 SHOULD (specification requirement term) 5 6665 SHOULD NOT (specification requirement term) 5 6666 SINCE (search key) 75 6667 SIZE (status item) 65 6668 SMALLER (search key) 75 6669 STARTTLS (command) 27 6670 STATUS (command) 63 6671 STATUS (response) 103 6672 STORE (command) 81 6673 SUBJECT (search key) 75 6674 SUBSCRIBE (command) 40 6675 Session Flag (class of flag) 12 6676 System Flag (type of flag) 11 6678 T 6679 TEXT (part specifier) 78 6680 TEXT (search key) 75 6681 TO (search key) 75 6682 TRYCREATE (response code) 95 6684 U 6685 UID (command) 85 6686 UID (fetch item) 80 6687 UID (fetch result) 111 6688 UID (search key) 75 6689 UIDNEXT (response code) 95 6690 UIDNEXT (status item) 64 6691 UIDNOTSTICKY (response code) 95 6692 UIDVALIDITY (response code) 95 6693 UIDVALIDITY (status item) 64 6694 UNANSWERED (search key) 75 6695 UNAVAILABLE (response code) 95 6696 UNDELETED (search key) 75 6697 UNDRAFT (search key) 75 6698 UNFLAGGED (search key) 75 6699 UNKEYWORD (search key) 75 6700 UNKNOWN-CTE (response code) 95 6701 UNSEEN (search key) 75 6702 UNSEEN (status item) 64 6703 UNSELECT (command) 70 6704 UNSUBSCRIBE (command) 41 6705 Unique Identifier (UID) (message attribute) 9 6707 X 6708 X (command) 87 6710 [ 6711 [RFC-5322] Size (message attribute) 13 6713 \ 6714 \All (mailbox name attribute) 101 6715 \Answered (system flag) 11 6716 \Archive (mailbox name attribute) 101 6717 \Deleted (system flag) 11 6718 \Draft (system flag) 12 6719 \Drafts (mailbox name attribute) 101 6720 \Flagged (mailbox name attribute) 101 6721 \Flagged (system flag) 11 6722 \HasChildren (mailbox name attribute) 100 6723 \HasNoChildren (mailbox name attribute) 100 6724 \Junk (mailbox name attribute) 101 6725 \Marked (mailbox name attribute) 100 6726 \Noinferiors (mailbox name attribute) 100 6727 \Noselect (mailbox name attribute) 100 6728 \Recent (system flag) 12 6729 \Seen (system flag) 11 6730 \Sent (mailbox name attribute) 101 6731 \Trash (mailbox name attribute) 101 6732 \Unmarked (mailbox name attribute) 100 6734 Authors' Addresses 6735 Alexey Melnikov (editor) 6736 Isode Ltd 6737 14 Castle Mews 6738 Hampton, Middlesex TW12 2NP 6739 UK 6741 Email: Alexey.Melnikov@isode.com 6743 Barry Leiba (editor) 6744 Huawei Technologies 6746 Phone: +1 646 827 0648 6747 Email: barryleiba@computer.org 6748 URI: http://internetmessagingtechnology.org/