Overview
- The outage began Thursday, Nov. 12, when users in the Americas first reported Exchange Online connectivity failures that spread to dozens of countries within an hour.
- Microsoft identified the root trigger as a subset of servers becoming unexpectedly unavailable, which increased load on the remaining infrastructure and caused widespread errors.
- The company has tracked the incident as EX1550543 and MO1550821 and has used traffic redistribution, deployment pauses, manual and automated server restarts as its main mitigation steps.
- Monitoring site Downdetector recorded a spike of about 130,000 Outlook-related reports at the peak and governments, courts and airlines reported real disruptions to email and customer channels.
- Microsoft reports initial stabilization and region-by-region recovery, says it has found no evidence of malicious activity, and has pledged a post-incident technical report once recovery is complete.