The hosting software on the server is called Direct Admin and in each hosted domain in Direct Admin I have set Spam Assassin to 5.0 (which I thought would be low enough to catch most spam).
I also configured it to allow all spam through but labelled as ***SPAM***.
I haven’t received a single email labelled as ***SPAM*** but I have received lots of spam. 😦
There’s obviously something simple missing in the config of SA on the server.
I know it is probably an impossible question to answer without more info but if anyone can think of something I might be missing, could you let me know?
UPDATE: A Direct Admin support staff member emailed me the fix – it is available at http://help.directadmin.com/item.php?id=36