Eric, the setup was identical to what I had in the first post, with the PF and NAT rules in place, SMTP proxy enabled in Simple mode, with my mail server definition in the routing tab. I see your point about the rules being disabled for the proxy to work, however nothing gets through if I do that (I'm testing from another email source). Not sure why.

The two emails that were detected were actual spam messages from an external source. One was blocked due to an RBL restriction, and the other was blocked due to a lack of reverse DNS lookup. There are 11 other emails in the SMTP log that originated from Astaro, however the 2 blocked were the only exceptions to that.

Also, since my last post, 5 more messages were blocked due to RBL and RDNS restrictions, however about 20 spam got through, and the number of spam on the Dashboard and "Mail Security" main page still is at 2. Strange.

It looks like the RBL and RDNS restrictions, take place before the SMTP proxy engine is actually doing any checking, and if it gets through the RBL check, mail is just offloaded to the mail server without any checks. I could be wrong, but with the 80 spam I received since last night, I would guess that it would have at least detected one of them.

I appreciate both of your advice on this, as I really want to get this working.