SpamAssassin Spam Filter

The SpamAssassin spam filter identifies spam messages among emails sent
to mailboxes hosted on your Plesk server.

Learn how to switch on and configure the spam protection at the
Switching on SpamAssassin section.

To achieve the desired level of spam protection, Plesk lets you
configure a number of SpamAssassin settings, namely:

• Spam filter sensitivity.

  To identify spam messages, SpamAssassin performs a number of
  different tests on contents and subject line of each message. As a
  result, each message scores a number of points. The higher the
  number, the more likely a message is spam. For example, a message
  containing the text string “BUY VIAGRA AT LOW PRICE!!!” in the
  Subject line and the message body scores 8.3 points. By default, the
  filter sensitivity is set so that all messages that score 7 or more
  points are classified as spam. If your users still receive spam
  messages with the default sensitivity, increase it by setting a
  lesser value, for example, 6. If SpamAssassin marks valid messages as
  spam, decrease the sensitivity by setting a higher value.

• Spam marks

  At the server level, you cannot set the server-wide spam filter to
  automatically delete spam: you can do it only on a per-mailbox basis.
  So, for the server-wide policy, you can choose only marking messages
  as spam: X-Spam-Flag: YES and X-Spam-Status: Yes headers are
  added to the message source by default. If you want, the spam filter
  will additionally include a specific text string to the beginning of
  the messages’ subject line (by default, this string is
  *****SPAM*****).

  Though you cannot configure SpamAssassin to delete all spam messages,
  you can let each mailbox owner configure their own spam protection
  settings. This includes, for example, setting their spam filters to
  automatically delete messages marked by SpamAssassin, or setting up
  their personal black and white lists. For details on adjusting spam
  filtering settings for a specific mailbox, refer to the section
  Protecting from Spam.

• Maximum size of messages to check

  Analyzing a huge number of emails can heavily increase the load on
  your server. To avoid this, you can set the maximum size of the
  message that the spam filter will test.

• Number of SpamAssassin processes

  Another way to limit the server loading by SpamAssassin is defining
  the maximum number of SpamAssassin processes (on Linux) or threads
  (on Windows) running simultaneously on the server.…