Found it & duh! It was already just farther down in that algorithm description quote - but upon realizing that I figured it was best to just make a new post for clarity.
Originally Posted by mmorse
auto_whitelist_factor n (default of 0.5, possible range of 0 to 1)
"How much towards the long-term mean for the sender to regress a message."
Basically, your tracking the long-term average spam scores of messages for the sender (mean).
Then, once the other checks have otherwise fully calculated the score for this message (aka preScore), AWL calculates the finalScore for the message as:
So if factor = 0.5, then it moves to half way between the calculated preScore and the mean. (toward the historyAverageScore)
finalScore = preScore + (mean - preScore) * factor
If factor = 0.3, then we'll move about 1/3 of the way from the score toward the mean.
The higher the value the closer toward using the stored historyAverageScore you are brought.
Thus a factor = 1 would be just to use the long-term average of all the SA scores.
And with a factor = 0 you're just using the calculated preScore....so it's a good alternative to turning use_auto_whitelist to 0 because you would still be creating the awl database but not acting on it yet.
So that would make my recommendation for first installs:
-use_auto_whitelist 0 for one week so that you work out SA rules as desired (also called sa_auto_whitelist=0)
-followed by a week of use_auto_whitelist 1 & auto_whitelist_factor 0 (to train the database)
-then increase the factor to 0.3 for another week (to start using the database)
-and factor of 0.5 from then on
UPDATE found the difference:
The $sa_auto_whitelist must be specified in amavisd.conf for SA versions older than 3.0, there was no equivalent options in local.cf. Starting with SA 3.0, there is now an option use_auto_whitelist to be specified in local.cf, and the $sa_auto_whitelist is ignored.
It would be even cooler to have something also consider the moving range, variance, & standard deviation; but you'd be adding precious CPU cycles. Of course, I'm sure there's stuff out there that does and boy I bet it's hard to develop the desired logic.