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The SPAM mail filter of SX-GATE classifies emails by identifying typical phrases
and other attributes indicating an unsolicited email. SX-GATE contains a database
of checks to perform and all matches result in a score which in turn allows filtering
emails. Characteristics indicating a SPAM mail will add a value to the score while other
characteristics indicating that it's not a SPAM mail will subtract a certain value. The
higher the final score, the more likely it's a SPAM mail.
Emails exceeding the size of 1MB will not be classified to save
system resources. However this is not a drawback, as a SPAM
mail is usually very small.
A few headers will be added to each email examined by the SPAM mail filter. The
header "X-Spam-Status" shows the final score (hits=...) and give the name of the
matches (tests=...). This allows the recipient of the mail to check the score of any mail.
The header "X-Spam-Level" will contain one "x" per scored point (e.g. "X-Spam-Level:
xxx" for a score between 3.0 and 3.99). This header allows automatic sorting in the
user's mail client or the SX-GATE webmail client.
Most mail clients will display only the most important headers
by default. Usually the full header information is available after
selecting a specific menu option.
Tag an email as SPAM when it is scored more than
If the score exceeds the threshold for tagging an email as SPAM, the subject of the
mail is prefixed by the text "******* SPAM *******". Furthermore the email will contain
a brief summary of the tests leading to this score. The original email is added as an
attachment.
Delivering the original email as attachment is supposed to achieve that selecting the
email in the mail client will not trigger any unwanted actions. Depending on the mail
client program used, the mere selection of an HTML formatted email may for example
trigger the download of images from the Internet as the mail client tries to show a
preview of the mail. So the sender of a SPAM mail is unnoticeably informed that the
SPAM mail was opened. This will increase the value of this email address for SPAM
mail senders and in turn more and more SPAM will be sent to this address.
Refuse to accept mails when score exceeds
Exceeding this threshold, SX-GATE's mail server will refuse to accept the email. The
sending system in charge of a proper reaction like e.g. notifying the sender or an
administrator. If you want to be sure that no requested email gets lost, you should not
enable this option. Activate the threshold "Tag an email as SPAM when it is scored
more than" instead and make use of the features offered by the mail client programs
to sort emails based on header lines.
