Microsoft Exchange Online Hit by Widespread Outage on August 31

Microsoft's Exchange Online service experienced a widespread outage on August 31, disrupting email and authentication for millions of users across the United States.

The issue, identified as EX1464935, caused emails to fail to send or arrive, along with connection problems in Outlook and authentication errors. Thousands of reports were recorded by Downdetector as the disruption spread.

Microsoft engineers isolated a common failure pattern involving authentication and protocol connectivity, but have not yet publicly identified the root cause. Some IT administrators speculate that an expired or improperly renewed certificate may be involved, although this has not been confirmed by Microsoft.

The outage is particularly concerning for businesses relying on Microsoft 365 as their primary email platform, as affected companies may have limited ability to resolve the issue from their own servers or networks.