[vox-tech] Mail server advice

[vox-tech@lists.lugod.org]

All right.  It looks like I'm getting a broadband connection again (DSL, it'll be nice to get my fix :)

This time I'll have a full DMZ, protected internal network etc.  However, I'd like to have a mail server that I can run off a Linux system (this will let me learn more about Linux).  I know that there are a couple of solutions out there that will fit my requirements but other than reading FAQs, I don't know anything about how good they actually are (I know Exchange).

Requirements
IMAP (I access from home and work so I like leaving things on the server)
Web mail
Spam Filtering.
Backup
The ability to act as a Secondary mail server for another domain.
List Server compatibilty(Probably Mailman)
Can handle multiple domains (I'll be hosting my mail and a friends)

Nice to have:  User Calenders

Now I realize that Linux/UNIX is to plug multiple packages together, and that's all good, but what packages/combo's should I be looking at?  I'm trying really hard to avoid Exchange  :)

Advise, links, pointers, personal experiances welcome
Thanks,
-sp

ps, sorry but some of the clients will probably be Outlook and Netscape Mail.