Linux Harbour

MailScanner is a free anti-virus and anti-spam filter running with MTA (Mail Transport Agent) on Linux systems, intergration with other anti-virus/spam software are required to provide these functions.

It highlights on its web site that it may protect over 1 billion e-mails every day, and it got 1 million dowloads. We did a number of Mailscanner installation on Debian and Fedora in past years.

Reference

HowToForge - Postfix Spam Filter using Ubuntu Dapper, MailScanner, SpamAssassin, Razor, Pyzor, DCC and ClamAV (Page2) (and page 3, 4, 5)

Anti-UCE at Postfix