CCS has opened a ticket with Microsoft regarding this issue, and we have received word that this is a global issue affecting multiple Office 365 environments. They are currently working to isolate the issue and fix it. The troubleshooting steps mentioned in our 10:15 status update can help, but some users are still seeing this issue after applying one of the two fixes. Microsoft will update us as soon as more information is available and we will share any updates received here.
The web-based GryphMail system accessible from the U of G website is unaffected by this issue - users who need immediate access to mail can sign in through the Students, Faculty, Staff Login link here: https://www.uoguelph.ca/