Question
How to enable SpamAssassin spam filter in Plesk?
Answer
Note: If Plesk Email Security extension is installed, SpamAssassin spam filter is enabled by default for all mailboxes.
Go to Tools & Settings > Spam Filter.
Enable Switch on server-wide SpamAssassin spam filtering.
Apply the changes.
Now SpamAssassin spam filter is enabled for all mailboxes in Plesk.
Note: To let Plesk users set their own spam filtering preferences on a per-mailbox basis, enable Apply individual settings to spam filtering. See the instructions below.

If the option Apply individual settings to spam filtering is enabled:
Go to Domains > example.com > Email Accounts > John Doe and switch to the Spam Filter tab.
Enable the setting Switch on spam filtering for this email address and choose what to do with spam emails.
Apply the changes.

Connect to a Plesk server via SSH (Linux) / RDP (Windows Server) and use these commands (on Windows Server, start a command prompt as an Administrator):
To enable SpamAssassin server-wide:
# plesk bin spamassassin --update-server -status true
To allow Plesk users manage spam filter settings for their email accounts:
# plesk bin spamassassin --update-server -personal-conf false
To switch on spam filtering for an email address:
# plesk bin spamassassin -u [email protected] -status true
Additional Information
- To improve the SpamAssassin spam filter accuracy by training it, visit this KB article.
- To test SpamAssassin spam filter, use the instructions from this KB article.
- To better protect a Plesk server from incoming spam, visit this KB article.