CDO is installed. The Exchange Web Services User Experience Monitor is a good idea but since it would be testing internal to internal mail routing rather than external to internal (which tests things getting stuck in an appliance) it wouldn't be possible to find certain failure conditions from external to internal. Is there another more simple user experience monitor, that you are aware of, to test emails flowing externally to internally that makes more sense to use than the MAPI user experience monitor?
I plan to take another look at the MAPI troubleshooting steps to see if I missed anything but since the MAPI profile works when called manually rather than when initiated from the SAM gui at first glance it seems it would be setup properly.