I was looking for:
- LDAP authentication
- POP3, POP3S, IMAP, IMAPS
- mbox support (simultaneous support for maildir is also nice since we'll hopefully migrate sometime soon.)
- easy but powerful configuration
- a nice responsive developer and support community
- uw-imap compatibility (that's what we were running before)
- written with security in mind
- good documentation
- open source and Free
We're using it here on two mailservers and I echo the above comments.
One other concern which worries me a little, is that the primary developer Timo seems to have gotten busy or uninterested recently. He was clearly going above and beyond by responding to every question within minutes, but looking at the archives recently he is posting a lot less. I just hope he's busy and not burned out because his work on dovecot is amazing.
He probably is busy but I kinda have the opposite perspective. Seems to me he got it into a shape where it was working quite well before going off and doing a lot of violence to the code for the next iteration. It's nice to have progress but stable checkpoints are good too. I dunno, can't have everything I guess :-)
If there were some real show-stoppers in what we're running now I'd probably have a different opinion.
mm