IMAP QRESYNC Extension (qresync)

Last modified: 2014-05-27


Applications Area Director

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The Internet Message Access Protocol (IMAP), defined in RFC 3501, specifies a protocol for accessing email messages on a server that implements a message store from a client. It also includes commands for manipulating the message store -- creating, deleting, and renaming mailboxes, adding a message to a mailbox, and copying messages from one mailbox to another.

Base IMAP as described in RFC 3501 requires that in order to discover flag changes and expunged messages in a mailbox, the client has to fetch flags for all messages it knows in the mailbox and compare returned results with its own state.

This can generate a significant amount of traffic for big mailboxes. The IMAP CONDSTORE extension (RFC 4551) provides a facility for IMAP clients to quickly resynchronize mailbox flag changes in a mailbox. The IMAP QRESYNC extension (RFC 5162) extends CONDSTORE to also cover expunged messages, and reduces the number of round trips needed to resynchronize by extending the SELECT/EXAMINE command.

The CONDSTORE and QRESYNC extensions are deployed in both clients and servers. These deployments have exposed errors and clarity issues in the specifications, and they need correcting. The IMAP QRESYNC Extension working group has the task of updating CONDSTORE and QRESYNC extensions on the Standards Track.

The working group might produce one (combined) or two separate documents (as now) updating these extensions. The working group will review errata and update the documents as needed to incorporate those, and will correct significant errors and inconsistencies, but will keep changes at this stage to a minimum and avoid incompatible changes.

No other IMAP extension work is in scope for this working group.

Goals and Milestones

Dec 2013 Request publication on updated qresync/condstore spec(s)

Request for Comments

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