After a bit of a scare with a zipped email attachment I am blocking .zip, .exe and .dll on our exchange server using a transport rule. To set it up I went to Organization Configuration, then Hub Transport, then the Transport Rules tab. I set up a rule to "Send bounce message to sender with enhanced status code". When I email a zipped file from within our domain I get the proper bounce back but when I send a zipped file from an external source the exchange server does not deliver the message and does not send the bounce back email. So the sender thinks the email was properly sent and the recipient doesn't know an email was sent. I have looked at the message tracking results and the external emails are reaching the exchange server but there is no results when searching for emails being sent back to that external address.
How can I make...