How to install SpamAssassin on a Plesk server?
From Plesk interface
Go to Tools & Settings > Updates > Add/Remove components > Mail hosting.
Note: for Plesk Onyx go to Tools & Settings > Updates and Upgrades > Add/Remove components > Mail hosting.
Mark the SpamAssassin component:
Press the Continue button.
From SSH/RDP server access
Note: If direct SSH/RDP access to the server is not possible, contact server administrator for further assistance.
Execute the following command:
# plesk installer –select-release-current –install-component spamassassin