PEP: SpamAssassin

SpamAssassin is a third party application that is used by many ISPs to filter mail. It works by analyzing both the headers and the body of a mail message and calculating a numeric score. The higher this score, the more likely it is to be spam.

Our mail servers automatically scan all mail and add a special header called X-Spam-Score: that contains a numeric spam score (the higher the number the more "spammy" the message is). For example:

X-Spam-Score: 12.5 (++++++++++++)

Because some filtering systems cannot perform numerical tests like PEP can, a simply bar graph is also included (one plus sign for each point).

If the spam score is 5.00 or higher than a second header named "X-Spam-Report:" is added that looks like this (yes, it spans multiple lines):

X-Spam-Report: Spam Assassin details:   (12.0 points, 5.0 required)
        pts rule name              description
        ---- ---------------------- --------------------------------------------------
        0.5 X_MSMAIL_PRIORITY_HIGH Sent with 'X-Msmail-Priority' set to high
        0.5 X_PRIORITY_HIGH        Sent with 'X-Priority' set to high
        4.4 DATE_SPAMWARE_Y2K      Date header uses unusual Y2K formatting
        1.6 RAZOR2_CF_RANGE_51_100 BODY: Razor2 gives confidence between 51 and 100
        [cf: 100]
        0.9 RAZOR2_CHECK           Listed in Razor2 (http://razor.sf.net/)
        1.4 DNS_FROM_RFCI_DSN      RBL: From: sender listed in dsn.rfc-ignorant.org
        1.2 MISSING_MIMEOLE        Message has X-MSMail-Priority, but no X-MimeOLE
        1.6 FORGED_MUA_OUTLOOK     Forged mail pretending to be from MS Outlook

Example

This example simply deletes all messages that score higher than 5.00:

delete if X-Spam-Score > 5.00