This tutorial demonstrate on how to adjust spam assassin score.

1. Login to Plesk Admin

2. At the left side click on Tools & Settings

3. Next search for Mail and Spam Filter

4. Once login it will show page Server-Wide Mail Settings and go to Spam Filtering

Do ensure to tick on (Switch on server-wide SpamAssassin spam filtering) 

5. Adjust the spam filter sensitivity by typing the desired value in the field and the score that a message must receive 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.

6. Lastly, click OK to apply the Spam Assassin scoring.