There is currently an issue with synchronizing Office 365 mail with the Mac Mail application. It is under investigation by Microsoft with their next information update scheduled for 4:00PM EDT on Friday, 4-Aug-2017.
Note that It may take a few days before the resolution is applied to all Office 365 customers. In the interim, Mac users can set up an imap account although this will only allow for mail synchronization and does not provide calendar access. Alternatively users can access Office 365 through the web portal by going to mail.uoguelph.ca or as a third option, they can install Outlook on their system.
We will post follow up information once Microsoft provides an update.
Anyone with questions or concerns can contact the service desk at 519.824.4120x58888 during regular office hours or by email to firstname.lastname@example.org