[stroths]

From pocket Outlook, Menu ->Tools -> Options -> Storage Tab. Check box to save attachments to your storage card.

You can also do some changes in your registry to change your documents folder to your storage card. This will make mail and everything document related go to storage. However, this caused issues in some previous devices as the SD went to sleep or couldn't wake up fast enough when the phone needed to access the documents folder. Might not be an issue on the TP.