Plesk server uses a score system in order to determine whether the received email should be forwarded to the mailbox or marked as spam.
1. Login to your Plesk server, either by manual login or login through your client area.
2. Then go to the Mail menu on the right.
3. Select the email for which you want to enable the spam filter.
4. Then activate the spam filter by checking "Switch on spam filtering...."
In this part of the action we strongly recommend to be marked / changed to the first and third menu only. Either mark the email with the title SPAM on it or move the email to the Spam folder. If using the delete option, the file will be deleted immediately and cannot be restored unless resent by the sender.
Then in the Advanced Settings option select the desired sensitivity. By default score 7 is a good starting number. If you receive an email whose score is above 7 or 7 then the email will be ACTIONed according to the provisions in the image above.
5. Then select what you want to do when you receive an email with a valid spam score.
6. Then click OK.
