According to UofT:
LATEST UPDATE TO CURRENT OUTAGE: (May 3rd, 2017 – 11:00 AM)
This is an update to the community in regards to the ongoing efforts to restore UTmail+ service. Microsoft has escalated the severity of the UTmail+ service issues to CRITICAL and is working to restore service as soon as possible.
At this time, Microsoft is unable to provide us with a service restoration timeline. The original target for restoration for Wednesday, May 3rd morning will not be met by Microsoft’s team. We apologize for the inconvenience this is causing to UTmail+ users.
Once this information is available we will post it immediately. Thank you for your ongoing patience.
Please see http://www.systemstatus.utoronto.ca/ for the latest updates.