I experimented several times during the holidays on various configurations of SpamAssassin and the like. I finally settled on something I liked and was easy to manage.
I found an addition to IPcop that added these services in a controllable manner – CopFilter – http://www.copFilter.org.
CopFilter plugs into IPcop and adds (for me) an SMTP proxy, ClamAV, SpamAssassin – as well as giving me a really simple web UI to manage things. Best of all all of the components are GPL.
I’ve trained the anti-spam – and it’s really working better so far than my own manual tweaking on a seperate server. 🙂
So far so good – I’ll keep track of the performance and post the results later.