Microsoft - Potential issues accessing mailboxes or sending email via one or more connection methods

Incident Report for McMaster University

Investigating

Microsoft is investigating a service-wide issue affecting Exchange Online. Some users may be unable to access their mailboxes or send email messages using Outlook on the web or desktop. This is not specific to McMaster.
Posted Oct 01, 2025 - 13:53 EDT
This incident affects: Microsoft Office 365 (Email).