1 Anti-Spam SMTP Proxy is a spam filter that sits on port 25 in front of your
2 regular SMTP server (sendmail, postfix, qmail, etc).
4 ASSP performs a number of configurable spam checks, and on detecting a spam
5 message, provides an immediate 5xx SMTP error code back to the client.
6 Non-spam messages are passed to your regular SMTP server for further
7 processing and delivery. ASSP includes SSL and IPv6 support. It is a single
8 script with a web-based configuration tool.
11 - a whitelist of known good senders
12 - Bayesian checks on message headers and contents
13 - recipient address validation using LDAP and RFC822 conformance
16 - SPF (Sender Policy Framework) checking
17 - DNSBL (DNS Block List) checking using many DNSBL services
18 - various SMTP error modes detection
20 and many other spam detection techniques.
22 WWW: http://assp.sourceforge.net/
23 WWW: http://opal.com/jr/freebsd/ports/mail/assp/