This feature is a SPAM whitelist feature correct? It merely doesn't flag the message as SPAM I thought. What I want is to deny all, then allow email only from a set list of addresses. This does that?
As a side note, personal settings for SPAM Assassin are not allowed on my server. If this feature does what I want then I could change this, but is there anyway to change the subject line modifier globally? My server default is to add [SPAM] at the beginning of the subject line, but if I enable user edits, then Plesk's user default is ****SPAM****. Why Plesk has two different defaults is strange, and I would like to keep the change transparent to my users.