I would go older rather than newer. Mature codebases are seldom as buggy as recently developed ones.

I'm looking at setting up a new instance of Citadel on a 32-bit ARM computer to see how well it works. When using the web frontend, the old BBS software runs comfortably in the background and just looks like forums, RSS feeds, Jabber (XMPP) instant messages, blogs, calendars (WebDAV) and emails.

The nice part (though only necessary on classic Amigas) is that it can run graphically on a custom client using its own protocol. On my own server I was going to experiment with bouncing external email sources so all the messages could be treated like an intranet in IMAP protocol unless there were admin privileges involved.

See the Citadel webpage for more information.