Thanks Stephen for the reply.
I noticed that when I use the >= predicate that it seems to work. I need to do some more testing.
I guess the initial problem stems from having multiple orchestrations pull email from the same mail box. So what I was thinking of doing was that I would have one receive port/location that would poll this inbox looking for messages of a particular keyword in the Subject. As mentioned I am using the TopXml POP3 receive adapter that allows for regular expressions. However it will just look for keywords in the message and then determine whether to down load where as what I was noticing in the filter expression it was only the standard predicates. What I did do was change the Receive port's keywords to include ROUTINE|TEST (so the subject must contain either ROUTINE or TEST for the email to be retrieved) I subsequently created two subscriptions…one for the ROUTINE 123456 emails to go to an orchestration and one that had "TESTS" go to a Send port subscription based upon the promoted property.
On the surface it looks like it is working, however I need to do some more testing as it almost seems too good to be true.
But, otherwise I may use the method that you described above.