amavisd-new!

Maia Mailguard is a web-based interface and management system based on the popular amavisd-new e-mail scanner and SpamAssassin. Written in Perl and PHP, Maia Mailguard gives end-users control over how their mail is processed by virus scanners and spam filters, while giving mail administrators the power to configure site-wide defaults and limits.

MailRoute provides a hosted service for mail protection from virus and spam.

MIMEDefang is an e-mail filtering tool that works with the Sendmail "Milter" library. MIMEDefang lets you express your filtering policies in Perl rather than C, making it quick and easy to filter or manipulate your mail.