I've just now discovered this part of the Plesk Administrator Guide:
Which application takes care of thie automatic removal? How can it be disabled?
Because all messages are automatically removed from the Spam folder after 30 days, you will need to review the contents of the Spam folder on a regular basis to make sure you do not miss any important messages, and move all non-spam messages back to the Inbox folder.
Which application takes care of thie automatic removal? How can it be disabled?