Hi heathu,
I tried this combination and it worked, but needs more tests in terms of what you want to do.
On Detection Exceptions, Add Exception -> Protocol "Protocol or Endpoint Monitoring" -> give it a name and tick Printer/Fax on Endpoint Destination.
Then select Also Match: Message Attachment or File Type Match -> click Add.
On Encapsulation Formats tick Microsoft Outlook Express (EML) and Microsoft Outlook (MSG, PST).
As i said, it needs more tests in terms of complience with your type and levels of protection, but in a simple test, it worked.
Regards