Mail Server Change – How the SPAM filtering is configured

Sent 2/28/2006



Now that I had a short nap here is some info on the new changes and how they affect SPAM.

You will notice that some of the emails will have a tag added to the subject line of SPAM-LOW or SPAM-MED. The new mail server has three threshold settings: Low, Medium & High. Those determinations are made by “weighting” each piece of mail.

For example we currently are assigning the following weights (links at the bottom that describe these type of tests:

Tests Weight

Bayesian Filtering 15
SPF-Pass -15
SPF-Fail 10
SPF-SoftFail 5
SPF-Neutral 0
SPF-PermError 0
SPF-None 0
Reverse DNS 10
Blacklists (RBL)
SpamCop 10
SpamHaus SBL-XBL 10

After an email get past these tests it will have a “score” and that score determines which threshold it has reached and what is to be done with the mail. A SPAM-LOW threshold is 20 and gets “tagged”, a SPAM-MED has a threshold of 30 and also gets tagged. A score of 40 indicates a SPAM-HIGH threshold and the message is deleted.

We will run with these settings for a few weeks to see how they compare to our previous results before we makeĀ  dditional changes. A friend of mine has been running his mail servers with these settings for about a month now and while SPAM does still get through the filters he has found it to be at a manageable level without any False Positives (mail tagged as spam and either held or deleted when it should not have been).

Bayesian Filtering



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