Spaminator is a server that is placed infront of your email server that allows you to take full advantage of the anti-virus/spam features while keeping your current email server intact.
Spaminator project provides a ready-to-use operating system configured to act as a spam filtering mail gateway.
This stage4 is a generic implementation of: http://www.gentoo.org/doc/en/mailfilter-guide.xml
Product's homepage
Here are some key features of "Spaminator":
· Real Time Black-Hole Lists
· ClamAV AntiVirus filtering
· Spam Assassin
· Postfix