Unix/Linux Mail Forwarder

I'm toying with the idea of setting up an SMTP gateway server on a Linux or Unix platform to catch spam and viruses before they reach the Exchange server. Here's what I've found so far:

How to configure a Linux mail server with SpamAssassin, MIMEDefang, and sendmail

Sendmail

FreeBSD (similar distribution to what sendmail was developed on, so it should be the most stable)

SpamAssasin

MIMEDefang

Welcome to Engrish.com!

Make laugh for the people much time!!!

Project Looking Glass Detailed View page

Oooh. Pretty. <drool>

Chaitin, Meta Math! The Quest for Omega

Good stuff. Had I but world enough and time . . .