How to check that SpamAssassin is protecting a Plesk server from spam?
Make sure that the SpamAssassin service is running at Tools & Settings > Services Management.
Make sure that the Switch on spam filtering for this email address option is enabled at Domains > example.com > Email Addresses > [email protected] > Spam Filter tab.
spamd: spamd: identified spam (1000.0/7.0) for [email protected]:110 in 6.1 seconds, 3926 bytes.
If all the above steps are successful – SpamAssassin is working fine.