Codingdomain.com

Automatic mail processing

Using SpamAssassin

With the xfilter command, Maildrop passes the e-mail message to another command. This can be used to filter spam through SpamAssassin.

SpamAssassin modifies the e-mail message, adding a few X-Spam- headers to the message. With an regular expression, Maildrop can move spam messages to a different folder.

Filtering Spam: ~/.mailfilter
# Unless an external MDA already filtered the message,
# let spamassassin modify the message first.
# Also continue if spamassassin fails.
#
if( ! /^X-Spam-Flag/  )
{
  exception {
    xfilter "/usr/bin/spamassassin -x"
  }
}


# SpamAssassin leaves a X-Spam-Flag field
# in the header, check for it
if(  /^X-Spam-Flag: YES/  )
{
  log "---- *SPAM* detected. "
  exception
  {
    # the exception clause causes maildrop to ignore errors
    to "$MAILBOX/.Spam/"
  }
}


# If these other headers are found, also
# move the message to the spam folder
#
if( (  /vdboor-remove_this/          ) \
||  (  /X-Mailer: Easy Mass Mailer/  ) \
||  (  /top--sites.net/              ) \
||  (  /staff@hotmail.com/           ) )
{
  log "---- *SPAM* manually filtered header"
  to "$MAILBOX/.Spam/"
}

Training

The filter of SpamAssassin can be trained with the sa-learn command. It needs to know which e-mail messages are considered spam, and which are normal messages (ham).

The sa-learn needs to know the folder where the messages are stored. For Courier IMAP, this folder location is a bit obscure. Subfolders start with a dot, read messages are stored in the "cur" folder, new messages are stored in the "new" folder.

Training the spam filter: 
sa-learn --showdots --ham  ~/.maildir/.codingdomain.vdboor/cur/
sa-learn --showdots --spam ~/.maildir/.Spam/cur/

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