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14.5.3 SPAM/Virus/Malware 367
of a regular email. Note however that this will not apply to many SPAM mails or
advertising.
In the text part there will be no formatting like e.g. colours or
different font sizes. Links will not be clickable, except the user's
mail client provides an automatic link detection. Furthermore
external resources loaded by an HTML mail while opening it will
be missing, too. This is however a nonserious bad practice (web
bugs).
The quality of the SPAM filter results may be reduced for emails
which have been altered by this feature.
14.5.3-H Relay SPAM filter
A SPAM mail is an unsolicited email, usually with dubious origin. The SPAM mail filter
tries to detect these emails and can be configured to tag these mails or refuse to accept
them.
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.