ASSP Spam Filter Gateway

The Anti-Spam SMTP Proxy (ASSP) Server project is an open source platform-independent SMTP Proxy server which implements whitelists and Bayesian filtering to rid the planet of the blight of unsolicited email (UCE). UCE must be stopped at the SMTP server. Anti-spam tools must be adaptive to new spam and customized for each site's mail patterns. This free, easy-to-use tool works with any mail transport and achieves these goals requiring no operator intervention after the initial setup phase.

• Easy browser-based setup (optional).
• Uses your existing message transport and existing SMTP server.
• Works with Sendmail, qmail, Postfix, Imail, Exchange, Courier, Mercury, Lotus Notes, and all other standard SMTP servers.
• Runs on Linux, Unix, Windows, OS X, OS/2, and more.
• Automatically customizes to your site's unique email profile.
• Automatic whitelist -- noone you email will ever be blocked.
• Senders receive immediate notification if mail is blocked but no erroneous bounces are ever generated.
• Redlist keeps an address off the whitelist.
• No-processing addresses pass through.
• Makes use of honeypot type spambucket addresses to automatically recognize spam and update your spam database.
• Bayesian filter intelligently classifies email into spam and non-spam.
• Supports additional site-defined regular expressions to identify spam or non-spam email.
• Can optionally block all non-whitelisted email (for anti-spam zelots).
• Mime encoded and other camouflaged spam is also recognized.
• Automatically maintains the spam and non-spam databases.
• Accepts whitelist submissions and spam error reports by authorized email.
• Optionally rejects executable attachments from non-whitelisted (or all) addresses.
• Free (as in speech) software -- Licensed under the GPL.
• Practically no maintenance required.
• Active user community and email list for support questions.
• Source code included if you need to customize your installation.
• Runs as a service in Windows NT / 2000.
• Optionally blocks no mail but adds an email header and/or updates the message subject.
• Optionally uses community-based spam statistics to identify hosts that are likely to send spam or non-spam mail.
• In *nix environments can switch to non-root user. Also supports chroot jail.
• Individual users can be configured to receive all mail.
• Shows detailed analysis of spam rating process for specific messages.
• Option to forward a copy of every rejected mail to an address.
• No perl modules to install -- runs complete "out of the box".
• Can block spam-bombs (when spammers forge your domain in the from field).
• Keeps spam statistics for your site.
• Detailed up-to-date documentation.
• Can listen on more than one smtp port.
• And much more!