IMAP QRESYNC Extension
charter-ietf-qresync-00-00

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. Both 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 as Proposed Standards. 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. In the event that implementation experience would
dictate an incompatible change to one (or both) of these extensions, the
corresponding IMAP capability identifiers would be changed.

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