For the last several months, I’ve been powering bit qua bit’s mail system with Citadel. In the yonder years, Citadel was a very powerful BBS for Unix systems. As the bulletin board days drew to a close, and its developers began searching for a way to keep Citadel relevant, they hit upon the idea of turning it into a groupware system. The current version of Citadel runs on most Unix platforms, supports secure IMAP, SMTP, and POP3 out of the box, provides the GroupDAV protocol for synchronizing with calendars and address books, and comes with a robust web client that lets you access everything when you’re away from your laptop.
Citadel’s been simply wonderful. Installing it under Debian Etch was trivial, involving little more than
apt-geting from their repository and answering a few very short questions. Integration with SpamAssassin involved little more than a few clicks, as do most administration tasks. Setting up restorable backups took all of five minutes, and making Citadel receive mail from multiple domains only took a bit longer. And, when I get really nostalgic, I can still connect to the system as if it were a text BBS to chat with users, perform administration tasks, or (not recommended) read my mail. (Use mutt if you want to go that route, as the Citadel text mail interface is gleefully unchanged from 1995 or so.)
Citadel’s hardly perfect. It gets a bit confused if your mail client tries to grab several IMAP folders at once; its web interface, though rich and functional, feels primitive; its
sendmail replacement is still under-featured; and setting up aliases is more confusing than it has to be. Still, I think it’s worth a look.