- RFC:2177 - IMAP4 IDLE command
- RFC:4551 - IMAP Extension for Conditional STORE Operation or Quick Flag Changes Resynchronization
- OfflineIMAP - a cache/replicator server
- Simulating IMAP over telnet
- Dovecot Secure IMAP Server - looks really interesting, and might replace my current IMAP server one day.
- Perdition, a IMAP/POP3 proxy for large-scale deployments
- binc - maildir-only, tries to follow the qmail way of doing things.
- isync, a mailbox synchronizer.
- IMAPsize (for Windows)
- IMAP tools - import, export, remove dupes, etc. Kinda buggy.
- imapsync - bulk migration, Perl style
Although most mobile phones have moderately decent e-mail clients, some of them are POP3-only or (as in the case of Motorola handsets) so poorly designed and useless that you wonder how their developers found a job in the first place, so it still makes sense to search for alternative IMAP clients.