SpamAssassin is a mail filter to identify spam. It is an intelligent email filter which uses a diverse range of tests to identify unsolicited bulk email, more commonly known as Spam. These tests are applied to email headers and content to classify email using advanced statistical methods. In addition, SpamAssassin has a modular architecture that allows other technologies to be quickly wielded against spam and is designed for easy integration into virtually any email system.

Features :

1. Header tests
2. Body phrase tests. For more information, see SpamAssassinRules.
3. Bayesian filtering (BayesFaq)
4. Automatic address whitelist/blacklist (AutoWhitelist)
5. Manual address whitelist/blacklist (ManualWhitelist)
6. Collaborative spam identification databases (DCC, Pyzor, Razor2); See NetworkTests.
7. DNS Blocklists, also known as "RBLs" or "Realtime Blackhole Lists". See DnsBlocklists
8. Character sets and locales

SpamAssassin's practical multi-technique approach, modularity, and extensibility continue to give it an advantage over other anti-spam systems. Due to these advantages, SpamAssassin is widely used in all aspects of email management. You can readily find SpamAssassin in use in both email clients and servers, on many different operating systems, filtering incoming as well as outgoing email, and implementing a very broad range of policy actions. These installations include service providers, businesses, not-for-profit and educational organizations, and end-user systems. SpamAssassin also forms the basis for numerous commercial anti-spam products available on the market today.