The UIDPLUS extension of the Internet Message Access Protocol (IMAP) provides a set of features intended to reduce the amount of time and resources used by some client operations. The features in UIDPLUS are primarily intended for disconnected-use clients.
You can read more about UIDPLUS at http://www.rfc-archive.org/getrfc.php?rfc=4315
Note that this RFC is dated December 2005 so may include some very recent proposals not in the original UIDPLUS RFC.
- Dovecot already supported UIDPLUS at one point for mbox, but implementing it for Maildir has to be done differently (UIDs are allocated later with Maildir). So currently the UIDPLUS code is removed until it can be made to work with Maildir.