Attachments get mailed inline base64 encoding

If a mail message comes into RT with an attachment it’s added to the
ticket history successfully and the attachment shown as a link. However,
when RT sends out that same message to the watcher or cc’s the
attachment becomes an inline base64 encoded ‘mess of characters’.

Snipet of what happens in the message:

------------=_1096621643-2484-2

Content-Type: application/octet-stream; name=“MDP.fdl”

Content-Disposition: inline; filename=“MDP.fdl”

Content-Transfer-Encoding: base64

PCBGTUYgMS4zID4KCjs7Ozs7Ozs7Ozs7Ozs7Ozs7Ozs7Ozs7Ozs7Ozs7Ozs7

Ozs7Ozs7Ozs7Ozs7Ozs7Ozs7Ozs7Cjs7Owo7OzsgICAgIFdPUktYUEVSVCBG

TE9XIERFRklOSVRJT04KOzs7Cjs7Ozs7Ozs7Ozs7Ozs7Ozs7Ozs7Ozs7Ozs7

Do I need to change a setting in my RT configuration, my rt-mailgate or
even at the exchange server?
Any suggestions please?
One of the biggest advantages of RT in our situation is this mail
oriented mode of operation.

Neville