SpamAssassin

SpamAssassin(tm) is a mail filter to identify spam. Using its rule base, it uses a wide range of heuristic tests on mail headers and body text to identify "spam", also known as unsolicited commercial email. The spam-identification tactics used include: header analysis: spammers use a number of tricks to mask their identities, fool you into thinking they've sent a valid mail, or fool you into thinking you must have subscribed at some stage. SpamAssassin tries to spot these. text analysis: again, spam mails often have a characteristic style (to put it politely), and some characteristic disclaimers and CYA text. SpamAssassin can spot these, too. blacklists: SpamAssassin supports many useful existing blacklists, such as mail-abuse.org, ordb.org or others. Once identified, the mail can then be optionally tagged as spam for later filtering using the user's own mail user-agent application.