davee, Exim now has a built in interface to spamd. That’s what I use and it’s also what we use on lug.org.uk. It’s very simple:

# put headers in all messages (no matter if spam or not)
warn  message = X-Spam-Score: $spam_score ($spam_bar)
      spam = nobody:true
warn  message = X-Spam-Report: $spam_report
      spam = nobody:true
  
# reject spam at high scores (> 12)
deny   message = This message scored $spam_score spam points.
       spam = nobody:true
       condition = ${if >{$spam_score_int}{120}{1}{0}}

You’ll need exim4-daemon-heavy on Debian sarge or etch.

I also recommend having some HELO checks before spamassassin, and virus checks after it. Exim can also call out to clamav to reject viruses at SMTP time.

Andrew, I’m a big fan of Xen myself, although using it is not something one consider lightly as it’s going to involve quite a lot of learning and effort on your part. What you want to do is easily achievable in Xen though 1GB really isn’t much RAM to be working with.

Pete, I would suggest making any inotify functionality completely optional, as some filesystems don’t support it and not all kernels have support either.

The fact that upstart doesn’t work without it is extremely annoying sometimes (last checked in Dapper; may have been fixed since).