ASSP or The Anti-Spam SMTP Proxy-server is a platform independent SMTP proxy server that implements whitelists, Bayesian spam filtering, and virus filtering to help stop unsolicited commercial email.
ASSP works on top of an existing SMTP server: it works with Sendmail, qmail, Postfix, and Imail, as well as Exchange, Courier, Mercury, and any standard SMTP server.
ASSP can run on a variety of operating systems, including Linux/Unix, OSX, Windows, and other systems.
Other functionality includes basic anti-virus capabilities through ClamAV virus database filtering, auto-whitelisting of known contacts, block bouncing, and multiple smtp port support.