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(See the Legal Provisions document at https://trustee.ietf.org/license-info for more information.) -- The document date (12 January 2022) is 128 days in the past. Is this intentional? 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: 'MESSAGELIMIT 1000' is mentioned on line 407, but not defined == Unused Reference: 'RFC7162' is defined on line 552, but no explicit reference was found in the text ** Obsolete normative reference: RFC 3501 (Obsoleted by RFC 9051) Summary: 2 errors (**), 0 flaws (~~), 2 warnings (==), 4 comments (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Network Working Group A. Melnikov 3 Internet-Draft Isode 4 Updates: 5267, 4731 (if approved) A. P. Achuthan 5 Intended status: Standards Track V. Nagulakonda 6 Expires: 16 July 2022 L. Alves 7 Yahoo! 8 12 January 2022 10 IMAP Paged SEARCH & FETCH Extension 11 draft-melnikov-imap-partial-02 13 Abstract 15 The PARTIAL extension of the Internet Message Access Protocol (RFC 16 3501/RFC 9051) allows clients to limit the number of search results 17 returned, as well as to perform incremental (paged) searches. This 18 also helps servers to optimize resource usage when performing 19 searches. 21 This document extends PARTIAL SEARCH return option originally 22 specified in RFC 5267. It also clarifies some interactions between 23 RFC 5267 and RFC 4731/RFC 9051. 25 This document also describes the MESSAGELIMIT extension for 26 announcing a limit on the number of messages that can be processed in 27 a single FETCH/SEARCH/STORE/COPY/MOVE command. 29 Status of This Memo 31 This Internet-Draft is submitted in full conformance with the 32 provisions of BCP 78 and BCP 79. 34 Internet-Drafts are working documents of the Internet Engineering 35 Task Force (IETF). Note that other groups may also distribute 36 working documents as Internet-Drafts. The list of current Internet- 37 Drafts is at https://datatracker.ietf.org/drafts/current/. 39 Internet-Drafts are draft documents valid for a maximum of six months 40 and may be updated, replaced, or obsoleted by other documents at any 41 time. It is inappropriate to use Internet-Drafts as reference 42 material or to cite them other than as "work in progress." 44 This Internet-Draft will expire on 16 July 2022. 46 Copyright Notice 48 Copyright (c) 2022 IETF Trust and the persons identified as the 49 document authors. All rights reserved. 51 This document is subject to BCP 78 and the IETF Trust's Legal 52 Provisions Relating to IETF Documents (https://trustee.ietf.org/ 53 license-info) in effect on the date of publication of this document. 54 Please review these documents carefully, as they describe your rights 55 and restrictions with respect to this document. Code Components 56 extracted from this document must include Revised BSD License text as 57 described in Section 4.e of the Trust Legal Provisions and are 58 provided without warranty as described in the Revised BSD License. 60 This document may contain material from IETF Documents or IETF 61 Contributions published or made publicly available before November 62 10, 2008. The person(s) controlling the copyright in some of this 63 material may not have granted the IETF Trust the right to allow 64 modifications of such material outside the IETF Standards Process. 65 Without obtaining an adequate license from the person(s) controlling 66 the copyright in such materials, this document may not be modified 67 outside the IETF Standards Process, and derivative works of it may 68 not be created outside the IETF Standards Process, except to format 69 it for publication as an RFC or to translate it into languages other 70 than English. 72 Table of Contents 74 1. Introduction and Overview . . . . . . . . . . . . . . . . . . 3 75 2. Document Conventions . . . . . . . . . . . . . . . . . . . . 3 76 3. The PARTIAL extension . . . . . . . . . . . . . . . . . . . . 3 77 3.1. Incremental SEARCH and partial results . . . . . . . . . 4 78 3.2. Interaction between PARTIAL, MIN, MAX and SAVE SEARCH 79 return options . . . . . . . . . . . . . . . . . . . . . 5 80 3.3. Extension to UID FETCH . . . . . . . . . . . . . . . . . 6 81 3.4. Use of PARTIAL and CONDSTORE IMAP extensions together . . 7 82 4. The MESSAGELIMIT extension . . . . . . . . . . . . . . . . . 7 83 4.1. Returning limits on the number of messages processed in a 84 single SEARCH/FETCH/STORE/COPY/MOVE command . . . . . . . 8 85 5. Formal syntax . . . . . . . . . . . . . . . . . . . . . . . . 10 86 6. Security Considerations . . . . . . . . . . . . . . . . . . . 11 87 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 11 88 7.1. Changes/additions to the IMAP4 capabilities registry . . 11 89 8. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 11 90 9. References . . . . . . . . . . . . . . . . . . . . . . . . . 12 91 9.1. Normative References . . . . . . . . . . . . . . . . . . 12 92 9.2. Informative References . . . . . . . . . . . . . . . . . 12 93 Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 94 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 13 96 1. Introduction and Overview 98 This document defines an extension to the Internet Message Access 99 Protocol [RFC3501] for performing incremental searches and fetches. 100 This extension is compatible with both IMAP4rev1 [RFC3501] and 101 IMAP4rev2 [RFC9051]. 103 The PARTIAL extension of the Internet Message Access Protocol (RFC 104 3501/RFC 9051) allows clients to limit the number of search results 105 returned, as well as to perform incremental (paged) searches. This 106 also helps servers to optimize resource usage when performing 107 searches. 109 This document extends PARTIAL SEARCH return option originally 110 specified in RFC 5267. It also clarifies some interactions between 111 RFC 5267 and RFC 4731/RFC 9051. 113 This document also describes the MESSAGELIMIT extension for 114 announcing a limit on the number of messages that can be processed in 115 a single FETCH/SEARCH/STORE/COPY/MOVE command. 117 2. Document Conventions 119 In protocol examples, this document uses a prefix of "C: " to denote 120 lines sent by the client to the server, and "S: " for lines sent by 121 the server to the client. Lines prefixed with "// " are comments 122 explaining the previous protocol line. These prefixes and comments 123 are not part of the protocol. Lines without any of these prefixes 124 are continuations of the previous line, and no line break is present 125 in the protocol unless specifically mentioned. 127 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 128 "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and 129 "OPTIONAL" in this document are to be interpreted as described in BCP 130 14 [RFC2119] [RFC8174] when, and only when, they appear in all 131 capitals, as shown here. 133 Other capitalised words are IMAP keywords [RFC3501][RFC9051] or 134 keywords from this document. 136 3. The PARTIAL extension 138 An IMAP server advertises support for the PARTIAL extension by 139 including "PARTIAL" capability in the CAPABILITY response/response 140 code. 142 Clients that implement support for PARTIAL extension MUST also 143 support the MESSAGELIMIT response code (see Section 4). 145 3.1. Incremental SEARCH and partial results 147 The PARTIAL search return option causes the server to provide in an 148 ESEARCH response a subset of the results denoted by the sequence 149 range given as the mandatory argument. The first result (message 150 with the lowest matching UID) is 1; thus, the first 500 results would 151 be obtained by a return option of "PARTIAL 1:500", and the second 500 152 by "PARTIAL 501:1000". This intentionally mirrors message sequence 153 numbers. 155 It is also possible to direct the server to start SEARCH from the 156 latest matching (with the highest UID) message. This can be done by 157 prepeding "-" to the index. For example -1 is the last message, -2 158 is next to the last and so on. Using this syntax helps server 159 implementations to optimize their SEARCHes. 161 A single command MUST NOT contain more than one PARTIAL or ALL search 162 return option -- that is, either one PARTIAL, one ALL, or neither 163 PARTIAL nor ALL is allowed. 165 For SEARCH results, the entire result list MUST be ordered in mailbox 166 order, that is, in UID or message sequence number order. 168 Where a PARTIAL search return option references results that do not 169 exist, by using a range which starts or ends higher (or lower) than 170 the current number of results, then the server returns the results 171 that are in the set. This yields a PARTIAL return data item that 172 has, as payload, the original range and a potentially missing set of 173 results that may be shorter than the extent of the range. If the 174 whole range references results that do not exist, a special value 175 "NIL" is returned by the server instead of the sequence set. 177 Clients need not request PARTIAL results in any particular order. 178 Because mailboxes may change, clients might wish to use PARTIAL in 179 combination with UPDATE (see [RFC5267] if the server also advertises 180 CONTEXT=SEARCH capability, especially if the intent is to walk a 181 large set of results; however, these return options do not interact 182 -- the UPDATE will provide notifications for all matching results. 184 // Let's assume that the A01 SEARCH without PARTIAL would return 185 // 23764 results. 186 C: A01 UID SEARCH RETURN (PARTIAL -1:-100) UNDELETED 187 UNKEYWORD $Junk 188 S: * ESEARCH (TAG "A01") UID PARTIAL (-1:-100 ...) 189 // 100 most recent results in set syntax elided. 190 S: A01 OK Completed. 192 // Let's assume that the A02 SEARCH without PARTIAL would return 193 // 23764 results. 194 C: A02 UID SEARCH RETURN (PARTIAL 23500:24000) UNDELETED 195 UNKEYWORD $Junk 196 C: A03 UID SEARCH RETURN (PARTIAL 1:500) UNDELETED 197 UNKEYWORD $Junk 198 C: A04 UID SEARCH RETURN (PARTIAL 24000:24500) UNDELETED 199 UNKEYWORD $Junk 200 S: * ESEARCH (TAG "A02") UID PARTIAL (23500:24000 ...) 201 // 264 results in set syntax elided, 202 // this spans the end of the results. 203 S: A02 OK Completed. 204 S: * ESEARCH (TAG "A03") UID PARTIAL (1:500 ...) 205 // 500 results in set syntax elided. 206 S: A03 OK Completed. 207 S: * ESEARCH (TAG "A04") UID PARTIAL (24000:24500 NIL) 208 // No results are present, this is beyond the end of the results. 209 S: A04 OK Completed. 211 3.2. Interaction between PARTIAL, MIN, MAX and SAVE SEARCH return 212 options 214 This section only applies if the server advertises PARTIAL IMAP 215 capability or CONTEXT=SEARCH [RFC5267], together with ESEARCH 216 [RFC4731] and/or IMAP4rev2"[RFC9051]. 218 The SAVE result option doesn't change whether the server would return 219 items corresponding to PARTIAL SEARCH result options. 221 As specified in Section 3.1, it is an error to specify both PARTIAL 222 and ALL result options in the same SEARCH command. 224 When the SAVE result option is combined with the PARTIAL result 225 option, and none of MIN/MAX/COUNT result options is present, the 226 corresponding PARTIAL is returned, and the "$" marker would contain 227 all messages returned by the PARTIAL result option. 229 When the SAVE + PARTIAL result options are combined with the MIN or 230 the MAX result option, and the COUNT result option is absent, the 231 corresponding PARTIAL result and MIN/MAX is returned (if the search 232 result is not empty), and the "$" marker would contain all messages 233 returned by the PARTIAL result option + the corresponding MIN/MAX 234 message. 236 If the SAVE + PARTIAL result options are combined with both MIN and 237 MAX result options, and the COUNT result options is absent, the 238 PARTIAL, MIN and MAX are returned (if the search result is not 239 empty), and the "$" marker would contain all messages returned by the 240 PARTIAL result option plus MIN and MAX messages. 242 If the SAVE + PARTIAL result options are combined with the COUNT 243 result option, the PARTIAL and COUNT are returned, and the "$" marker 244 would always contain all messages found by the SEARCH or UID SEARCH 245 command. 247 The following table summarizes the additional requirement on ESEARCH 248 server implementations described in this section. 250 +==============================+=====================+ 251 | Combination of Result option | "$" marker value | 252 +==============================+=====================+ 253 | SAVE PARTIAL | PARTIAL | 254 +------------------------------+---------------------+ 255 | SAVE PARTIAL MIN | PARTIAL & MIN | 256 +------------------------------+---------------------+ 257 | SAVE PARTIAL MAX | PARTIAL & MAX | 258 +------------------------------+---------------------+ 259 | SAVE PARTIAL MIN MAX | PARTIAL & MIN & MAX | 260 +------------------------------+---------------------+ 261 | SAVE PARTIAL COUNT [m] | all found messages | 262 +------------------------------+---------------------+ 264 Table 1 266 where '[m]' means optional "MIN" and/or "MAX" 268 3.3. Extension to UID FETCH 270 The PARTIAL extension also extends the UID FETCH command with a 271 PARTIAL FETCH modifier. The PARTIAL FETCH modifier has the same 272 syntax as the PARTIAL SEARCH result option. Presence of the PARTIAL 273 FETCH modifier instructs the server to only return FETCH results for 274 messages in the specified range. It is useful when the sequence-set 275 (first) parameter to the UID FETCH command includes unknown number of 276 messages. 278 // Returning information for the last 3 messages in the UID range 279 C: 10 UID FETCH 25900:26600 (UID FLAGS) (PARTIAL -1:-3) 280 S: * 12888 FETCH (FLAGS (\Seen) UID 25996) 281 S: * 12889 FETCH (FLAGS (\Flagged \Answered) UID 25997) 282 S: * 12890 FETCH (FLAGS () UID 26600) 283 S: 10 OK FETCH completed 285 // Returning information for the first 5 messages in the UID range 286 C: 11 UID FETCH 25900:26600 (UID FLAGS) (PARTIAL 1:5) 287 S: * 12591 FETCH (FLAGS (\Seen) UID 25900) 288 S: * 12592 FETCH (FLAGS (\Flagged) UID 25902) 289 S: * 12593 FETCH (FLAGS (\Answered) UID 26310) 290 S: * 12594 FETCH (FLAGS () UID 26311) 291 S: * 12595 FETCH (FLAGS (\Answered) UID 26498) 292 S: 11 OK FETCH completed 294 3.4. Use of PARTIAL and CONDSTORE IMAP extensions together 296 This section is informative. 298 The PARTIAL FETCH modifier can be combined with the CHANGEDSINCE 299 FETCH modifier. 301 // Returning information for the last 30 messages in the UID range 302 // that have any flag/keyword modified since modseq 98305 303 C: 101 UID FETCH 25900:26600 (UID FLAGS) (PARTIAL -1:-30 CHANGEDSINCE 98305) 304 S: * 12888 FETCH (FLAGS (\Flagged \Answered) MODSEQ (98306) UID 25997) 305 S: * 12890 FETCH (FLAGS () MODSEQ (98312) UID 26600) 306 S: 101 OK FETCH completed 308 The above example causes the server to first select the last 30 309 messages and then only return flag changes for subset of these 310 messages which have MODSEQ higher than 98305. 312 Note that the order of PARTIAL and CHANGEDSINCE FETCH modifiers in 313 the UID FETCH command is not important, i.e. the above example can 314 also use "UID FETCH 25900:26600 (UID FLAGS) (CHANGEDSINCE 98305 315 PARTIAL -1:-30)" command and it would result in the same responses. 317 4. The MESSAGELIMIT extension 319 An IMAP server advertises support for the MESSAGELIMIT extension by 320 including "MESSAGELIMIT=" capability in the CAPABILITY 321 response/response code, where "" is a positive integer that 322 conveys the maximum number of messages that can be processed in a 323 single SEARCH/FETCH/STORE/COPY/MOVE command. 325 4.1. Returning limits on the number of messages processed in a single 326 SEARCH/FETCH/STORE/COPY/MOVE command 328 // Do we need a way to specify SEARCH criterion for "all UIDs after" 329 // or "all UIDs before" a specific UID? 331 If a server implementation doesn't allow more than messages to be 332 operated on by a single SEARCH/FETCH/STORE/COPY/MOVE command, it MUST 333 return the MESSAGELIMIT response code defined below: 335 MESSAGELIMIT The server doesn't allow more than messages to be operated 336 on by a single SEARCH/FETCH/STORE/COPY/MOVE command. The 337 lowest processed UID is . The client needs to repeat 338 the operation for remaining messages, if required. 340 In the following example the value is 1000 and the lowest 341 processed UID is 23221. 343 C: 03 FETCH 10000:14589 (UID FLAGS) 344 S: * 14589 FETCH (FLAGS (\Seen) UID 25000) 345 S: * 14588 FETCH (FLAGS (\Answered) UID 24998) 346 S: ... further 997 fetch responses 347 S: * 13590 FETCH (FLAGS () UID 23221) 348 S: 03 OK [MESSAGELIMIT 1000 23221] FETCH completed with 1000 partial 349 results 351 In the following example the client searches for UNDELETED UIDs 352 between 22000:25000. The total number of matching messages 353 exceeds the server's published 1000 messages limit. 355 C: 04 UID SEARCH UID 22000:25000 UNDELETED 356 S: * SEARCH 25000 24998 (... 997 UIDs ...) 23221 357 S: 04 OK [MESSAGELIMIT 1000 23221] SEARCH completed with 1000 partial results 359 The following example demonstrates copy of messages with UIDs 360 between 18000:21000. The total message count exceeds the 361 server's published 1000 messages limit. 363 C: 05 UID COPY 18000:21000 "Trash" 364 S: * NO [MESSAGELIMIT 1000 20001] Too many messages to copy 365 S: 05 OK [COPYUID 1397597919 20001:21000 21363:22362] COPY completed for the last 1000 messages 367 // Open Issue: 369 The following example shows MOVE of messages with UIDs between 370 18000:21000. The total message count exceeds the server's 371 published 1000 messages limit. The client that wants to move 372 all messages in the range and observes a MESSAGELIMIT response 373 code, can repeat the command by updating the UID set parameter 374 specified in the command. The client needs to keep doing this 375 until MESSAGELIMIT response is not returned (or until a tagged 376 NO/BAD is returned). 378 C: 06 UID MOVE 18000:21000 "Archive/2021/2021-12" 379 S: * OK [COPYUID 1397597919 20001:21000 22363:23362] Some messages were not moved 380 S: * 12336 EXPUNGE 381 S: * 12335 EXPUNGE 382 ... 383 S: * 11335 EXPUNGE 384 S: 06 OK [MESSAGELIMIT 1000 20001] MOVE completed for the last 1000 messages 386 The following example shows update of flags for messages with 387 UIDs between 18000:20000. The total message count exceeds the 388 server's published 1000 messages limit. The client that wants 389 to change flags for all messages in the range and observes a 390 MESSAGELIMIT response code, can repeat the command by updating 391 the UID set parameter specified in the command. The client 392 needs to keep doing this until MESSAGELIMIT response is not 393 returned (or until a tagged NO/BAD is returned). 395 C: 07 UID STORE 18000:20000 +FLAGS (\Seen) 396 S: * 11215 FETCH (FLAGS (\Seen \Deleted) UID 20000) 397 S: * 11214 FETCH (FLAGS (\Seen \Answered \Deleted) UID 19998) 398 ... 399 S: * 10216 FETCH (FLAGS (\Seen) UID 19578) 400 S: 07 OK [MESSAGELIMIT 1000 19578] STORE completed for the last 1000 messages 402 The following example shows use of MESSAGELIMIT response code 403 together with the PARTIAL extension. The total message count 404 exceeds the server's published 1000 messages limit. 406 C: 08 UID FETCH 22000:25000 (UID FLAGS MODSEQ) (PARTIAL -1:-1500) 407 S: 08 NO [MESSAGELIMIT 1000] FETCH exceeds the maximum 1000 message limit 409 Note that when the server needs to return both EXPUNGEISSUED 410 ([RFC9051]) and MESSAGELIMIT response codes, the former MUST be 411 returned in the tagged OK response, while the latter MUST be returned 412 in an untagged NO response. The following example demonstrates that: 414 C: 031 FETCH 10000:14589 (UID FLAGS) 415 S: * 14589 FETCH (FLAGS (\Seen) UID 25000) 416 S: * 14588 FETCH (FLAGS (\Answered) UID 24998) 417 S: ... further 997 fetch responses 418 S: * 13590 FETCH (FLAGS () UID 23221) 419 S: * NO [MESSAGELIMIT 1000 23221] FETCH completed with 1000 partial 420 results 421 S: 031 OK [EXPUNGEISSUED] Some messages were also expunged 423 5. Formal syntax 425 The following syntax specification uses the Augmented Backus-Naur 426 Form (ABNF) notation as specified in [ABNF]. 428 Non-terminals referenced but not defined below are as defined by 429 IMAP4 [RFC3501]. 431 Except as noted otherwise, all alphabetic characters are case- 432 insensitive. The use of upper or lower case characters to define 433 token strings is for editorial clarity only. Implementations MUST 434 accept these strings in a case-insensitive fashion. 436 SP = 437 MINUS = "-" 439 capability =/ "PARTIAL" 440 ;; from [RFC3501] 442 modifier-partial = "PARTIAL" SP partial-range 444 partial-range-first = nz-number ":" nz-number 445 ;; Request to search from oldest (lowest UIDs) to 446 ;; more recent messages. 447 ;; A range 500:400 is the same as 400:500. 448 ;; This is similar to from [RFC3501], 449 ;; but cannot contain "*". 451 partial-range-last = MINUS nz-number ":" MINUS nz-number 452 ;; Request to search from newest (highest UIDs) to 453 ;; oldest messages. 454 ;; A range -500:-400 is the same as -400:-500. 456 partial-range = partial-range-first / partial-range-last 458 search-return-opt =/ modifier-partial 459 ;; All conform to , from [IMAP-ABNF]/[RFC9051] 461 search-return-data =/ ret-data-partial 463 ret-data-partial = "PARTIAL" 464 SP "(" partial-range SP partial-results ")" 465 ;; is the requested range. 467 partial-results = sequence-set / "NIL" 468 ;; from [RFC3501]. 469 ;; NIL indicates no results correspond to the requested range. 471 tagged-ext-simple =/ partial-range-last 473 fetch-modifier =/ modifier-partial 475 capability =/ "MESSAGELIMIT=" message-limit 476 ;; from [RFC3501] 478 message-limit = nz-number 480 resp-text-code =/ "MESSAGELIMIT" SP message-limit [SP uniqueid] 481 ;; No more than nz-number messages can be processed 482 ;; by any command at a time. The last (lowest) processed 483 ;; UID is uniqueid. 484 ;; The last parameter is omitted, when not known. 486 6. Security Considerations 488 TBD. 490 7. IANA Considerations 492 7.1. Changes/additions to the IMAP4 capabilities registry 494 IMAP4 capabilities are registered by publishing a standards track or 495 IESG approved Informational or Experimental RFC. The registry is 496 currently located at: 498 https://www.iana.org/assignments/imap4-capabilities 500 IANA is requested to add definition of the PARTIAL extension to point 501 to this document. 503 8. Acknowledgments 505 This document was motivated by Yahoo! team and their questions about 506 best client practices for dealing with large mailboxes. 508 Editor of this document would like to thank the following people who 509 provided useful comments or participated in discussions of this 510 document: Timo Sirainen. 512 This document uses lots of text from RFC 5267. Thus work of the RFC 513 5267 authors Dave Cridland and Curtis King is appreciated. 515 9. References 517 9.1. Normative References 519 [ABNF] Crocker, D., Ed. and P. Overell, Ed., "Augmented BNF for 520 Syntax Specifications: ABNF", RFC 5234, January 2008, 521 . 523 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 524 Requirement Levels", BCP 14, RFC 2119, 525 DOI 10.17487/RFC2119, March 1997, 526 . 528 [RFC3501] Crispin, M., "INTERNET MESSAGE ACCESS PROTOCOL - VERSION 529 4rev1", RFC 3501, DOI 10.17487/RFC3501, March 2003, 530 . 532 [RFC4731] Melnikov, A. and D. Cridland, "IMAP4 Extension to SEARCH 533 Command for Controlling What Kind of Information Is 534 Returned", RFC 4731, DOI 10.17487/RFC4731, November 2006, 535 . 537 [RFC5267] Cridland, D. and C. King, "Contexts for IMAP4", RFC 5267, 538 DOI 10.17487/RFC5267, July 2008, 539 . 541 [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 542 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, 543 May 2017, . 545 [RFC9051] Melnikov, A., Ed. and B. Leiba, Ed., "Internet Message 546 Access Protocol (IMAP) - Version 4rev2", RFC 9051, 547 DOI 10.17487/RFC9051, August 2021, 548 . 550 9.2. Informative References 552 [RFC7162] Melnikov, A. and D. Cridland, "IMAP Extensions: Quick Flag 553 Changes Resynchronization (CONDSTORE) and Quick Mailbox 554 Resynchronization (QRESYNC)", RFC 7162, 555 DOI 10.17487/RFC7162, May 2014, 556 . 558 Index 560 M 562 M 564 MESSAGELIMIT (response code) 565 Section 4.1, Paragraph 3.2.1 567 Authors' Addresses 569 Alexey Melnikov 570 Isode Limited 572 Email: alexey.melnikov@isode.com 573 URI: https://www.isode.com 575 Arun Prakash Achuthan 576 Yahoo! 578 Email: arunprakash@myyahoo.com 580 Vikram Nagulakonda 581 Yahoo! 583 Email: nvikram_imap@yahoo.com 585 Luis Alves 586 Yahoo! 588 Email: luis.alves@lafaspot.com