On Thursday, Microsoft 365 servers kept failing their health checks and Outlook went down for 100,000+ people. The fix, in Microsoft's words: We've validated an alternative health check method. Your turn.
The checks, the log and the verdicts are invented. These are not.
On Thursday, November 12, 2026, a Microsoft 365 outage hit Outlook, Teams, SharePoint Online, Microsoft 365 Copilot and Defender XDR. Microsoft says the incident began at 1:26 PM ET. BleepingComputer, Nov 12, 2026
Microsoft: “We determined the elevated load isn't driven by an increase in traffic, but by a number of servers being unexpectedly unavailable; straining the remaining infrastructure.” BleepingComputer
Microsoft's status page said servers were failing automated health checks, that the failures “may originate from a specific component on the affected servers that's responsible for processing them,” and that it was “deploying a targeted change to bypass this component.” Tom's Guide
Then: “We've validated an alternative health check method on a subset of affected infrastructure, which allowed the servers in that subset to successfully return to service, and we're now applying this change more broadly.” Tom's Guide
To be fair to Microsoft: by its account, the old check was the broken part, so swapping it was a real fix. Swapping yours is not.