Anti-spam protection

To protect against unsolicited email (a spam) the built-in mail client filter can be used. However even more effective solution is the filter placed on a mail server.

There are two ways of the filter usage ("Spam filter mode" field): immediate spam removal and message marking with special headers. The latest variant is the most preferable. On the one hand, this saves machine resources (by not starting a local filter), on the other, each user can decide himself what is considered as spam and how it is processed.

The filter analyzes a letter on many criteria and set it a final score. The higher it is, the more probability that letter is a spam. "Required score" parameter defines starting value, from which the letter will be recognized as a spam and, for example, removed. Letter evaluation criteria can be set independently with the name of the rule and it's score.

"Score" is calculated from one or four numbers.

RULE_NAME 0.5
RULE_NAME 0.5 0.6 0.5 0.5
RULE_NAME (0.2) (0.3) (0.2) (0.2)

One number means final rule score. If four numbers are specified, one of them is choosed depending on use or non-use of a statistical (on the Bayes algorithm basis) and network analyzers.

  statistical
noneuse
networknone 1st 3rd
use 2nd 4th

If the number is in parentheses, it will be added to the already counted rule score.

Senders whitelist allows to estimate their reliability in long-term prospect.