I know it applies to OL 2010 but I just can't find anything for OL 2013
Exact same steps in '2013 - have you tried or just assuming it's different? If your ribbon in '2013 isn't the same as the following after opening a previously sent message then suggest you post a screenshot of what you have

Karl Timmermans [Outlook MVP] "Outlook Contact Import/Export/Data Mgmt" http://www.contactgenie.com