SpamAssassin Concepts, pt.2 


Combines many systems for a "broad-spectrum" approach:

Detect forged headers

Spam-tool signatures (Message-ID patterns etc.)

Text keyword scanner in the message body (Viagra etc.)

DNS blacklists

Razor, DCC (Distributed Checksum Clearinghouse), Pyzor

Spammers cannot aim to defeat 1 system; the others will catch them out