Take back control of your email with this mail server in a box
Provides mechanisms for walking through any arbitrary PHP variable
Next Generation Open Source Firewall
Anti Spam SMTP Gateway
An easy-to-use anti-spam email gateway
Easy installation and configuration of a complete mail server
The free cross-platform antivirus software tool-kit
Virtual Appliance of RadicalSpam
Open Source Anti-Spam and Anti-Virus Gateway
javascript to convert thunderbird/seamonkey filters to sieve rules
AV/content filter for Qmail
File scanning spam filter MDaemon plugin.