Qmail and Friends (a.k.a. I'm in London but my Mail is in Dallas) 

I just spent a day down in the mental Geek Zone installing yet another
Qmail/filtering/IMAP system. Now both of my
Rimu hosts are running fully customised mail exchangers. I've typed up
some brief notes on the topic.
I've been pleasantly surprised how easy it is to run the
Apple Mail program with a totally remote IMAP mail repository; the Mail program can even be persuaded to map its draft and trash folders to IMAP. One needs a pretty solid broadband line to deal with all the caching and synchronisation, but it works pretty well.
I'm actually running IMAPS (i.e. SSH encryption), which is probably breaking various EU laws - certainly, my incoming email cannot be read in accordance with the
EU data retention laws. I'm toying with bringing up a VPN to protect my outgoing mail as well.