Description:

Mail Avenger - The spam extermination project
Mail Avenger is a highly-configurable, MTA-independent SMTP server daemon.
It lets users run messages through filters like ClamAV and SpamAssassin
during SMTP transactions, so the server can reject mail before assuming
responsibility for its delivery. Other unique features include TCP SYN
fingerprint and network route recording, verification of sender addresses
through SMTP callbacks, SPF (sender policy framework) as a general policy
language, qmail-style control over both SMTP-level behavior and local
delivery of extension addresses, mail-bomb protection, integration with
kernel firewalls, and more.