=The Auto-Whitelist =

The auto-whitelist, or AWL, tracks scores for your regular correspondents in a small on-disk database. It is enabled using the -a flag to spamassassin or spamd.

The AWL is actually a very simple system. In short, the AWL is a score averaging system. It keeps track of the historical average of a sender, and pushes any subsequent mail towards that average.

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If that same person sent you a mail that scored 0, and then later sent one that scored 7, the AWL would push the score down to 3.5. This is auto-whitelisting based on past history of nonspam.

A "sender" is identified using both the address they sent with, and their IP address, so spam claiming to be From you with forged headers will fail to get through.

But the "auto whitelist" isn't really a whitelist per-se. . It does however have a "learning white/blacklist" type behavior as a result of it's averaging.

Sometimes it may appear that the AWL is assigning scores the wrong way; read AwlWrongWay for details.

How Does It Work?

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The algorithm works using a database of entries. Each entry has a key formed by the From: address of the mail, and the IP address it originated at, and contains a TOTAL score and a COUNT number. The MEAN score is TOTAL/COUNT. The current algorithm works as follows:

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