Overview
- User reports spiked Thursday evening as Exchange/Outlook access problems emerged in the U.S. and then spread to Microsoft 365 services worldwide.
- Microsoft says an unusually large number of servers became unavailable after automated health checks tied to one component failed, and the company is still investigating the root cause.
- To limit impact Microsoft halted new deployments, rerouted traffic away from affected systems, restarted impacted servers, tested targeted configuration changes, and applied bypasses for the suspected component.
- Downdetector showed roughly 130,000 Outlook problem reports at the peak and later recorded a decline to about 50,000 reports as mitigations took effect.
- Enterprise customers are directed to the Microsoft 365 Admin Center and public status pages under incident IDs EX1550543 and MO1550821 for technical details and ongoing updates.