What happens to spam?
In Version 2.x of the 42go ISP-Manager you can specify if spam should be delivered to the recipient ("Accept"; the subject will be rewritten to indicate spam so that email filtering can be done by the recipient's email client) or if it should be deleted.
In Version 1.x of the 42go ISP-Manager spam is deleted immediately (without being buffered).
Knowing that, you should only use the spam filter if you are sure (e.g. after a little testing period), that it classifies your emails correctly to a high degree, i.e., that it does not delete important emails!