NoSpamToday! and Automatic Address Whitelists
NoSpamToday! is a range of powerful anti-spam products that use the award-winning open source spam filter SpamAssassin. Easy to setup, NoSpamToday! requires no more than a couple of mouse-clicks to install on Windows servers or workstations.
Essentially, SpamAssassin is an intelligent email filter which uses a wide range of tests to identify spam. With the help of rulesets, blackhole lists and Bayesian filtering, it checks things such as email headers and content. SpamAssassin also includes something known as the automatic whitelist or AWL.
This automatic address whitelist keeps track of the people who send you emails, and uses a score averaging system to determine whether new messages from them might contain spam. Thanks to the automatic whitelist, their past history can either work for or against them. If a previously unknown person sends you an email that scores 0 (i.e. not very likely to be spam), this is noted on the AWL database. If this person then sends you another message that would normally score a 10 (i.e. probably spam), their previous history of "clean" messages would work in their favor, and the score would be pushed down to 5.
