Overview
- Microsoft reported a major outage on Thursday, Nov. 12 that began with users unable to access Exchange Online mailboxes and then spread to other Microsoft 365 services.
- Outage trackers logged a sharp surge of user reports, roughly 120,000–140,000 at the peak, showing large-scale interruptions for Outlook and related apps.
- The company says the problem came from a number of servers becoming unexpectedly unavailable, which raised load on remaining infrastructure and caused automated health checks to fail.
- Engineers have paused deployments, restarted affected servers, redistributed connection traffic, tested a health-check bypass and prepared automated restarts while monitoring results.
- Microsoft is still investigating with no public evidence of a cyberattack, and administrators can follow incident advisories under EX1550543 and MO1550821 in the Microsoft 365 admin center.