To switch on SpamAssassin:

  • Go to Tools & Settings > Spam Filter Settings (in the Mail group).
  • Select the option Switch on server-wide SpamAssassin spam filtering.
  • To let your users set their own spam filtering preferences on a per-mailbox basis, select the option Apply individual settings to spam filtering.
  • Specify the maximum number of SpamAssassin processes in the field Maximum number of worker spamd processes to run (1-5). We recommend that you use the default value.
  • Adjust the spam filter's sensitivity by typing the desired value in the field The number of points a message must score to qualify as spam.

    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.

  • On Windows, define the maximum size of messages that SpamAssassin will process by selecting the option Do not filter if mail size exceeds specified size and providing the desired value. On Linux, this parameter is unavailable in Plesk. 
  • Specify how to mark messages recognized as spam in the field Add the following text to the beginning of subject of each message recognized as spam. If you do not want the spam filter to modify message subject, leave this box blank. 
  • On Windows, specify trusted languages and locales using the lists Trusted languages and Trusted locales.
  • Click OK.