Thanks Bob. I double checked the domain spelling and it is correct.

I tried disabling the packet filter and DNAT, however that stopped mailflow completely.

Over the course of the night, there were 2 reported spam messages, so it appears something is happening. On the main "Mail Security" page that shows the current days statistics, it shows a current value of 13 MB, with an average of 24 MB.

This indicated mail is going through the proxy, right? Also, in the daily notification report, it only shows 2 messages total were processed. Is the total number the amount filtered, or should it match the total number of emails I've received?

The discouraging part is I have received about 50 spam in that time, where only 2 were marked as such.