MAC Computer issue
On Office for MAC version 2016 Outlook you may notice your email stopped synchronizing your emails or not sending out email. Your outbox have mail not sent.
If that happens you must make sure you have a connection to the network.
If you have connection to the network verify you user name and password is correct from your Queens account settings
see this article:
If that is correct check the following settings in tools menu.
This is a slider that toggles online and offline. Ensure it is set to online.