I have a single user that cannot send email from the Mac after migrating to Exchange 2013 on-prem. I myself am on the same Exchange server and am using a Mac with Office 2011 and am able to send/receive emails without any issues.

When the user sends an email it goes to the sent mail folder and syncs with the server and can be seen on a windows machine running any other version of Office (same in OWA). I've logged the user in on my Mac and blown away my profile and seeing the same issue.

I do not see anything in the logs on the server and have not seen any error son the Mac.

Any thoughts as to where my issues is?