What Caused the Microsoft 365 Outage of November 12, 2026
The Microsoft 365 outage that began on November 12, 2026 was caused, according to Microsoft’s status updates, by servers in the Exchange Online service unexpectedly failing automated health checks and dropping out of service, which pushed more load onto the servers that remained until they were overwhelmed too. Microsoft has said the load was not caused by a rise in traffic, has reported no…
The Microsoft 365 outage that began on November 12, 2026 was caused by servers in the Exchange Online service unexpectedly failing automated health checks and dropping out of service, which pushed more load onto the remaining servers until they too became overwhelmed. Microsoft has stated that the load was not caused by a rise in traffic or any malicious activity, and has not yet published a post-incident review to determine the underlying trigger.
The incident caused degradation of various Microsoft 365 services worldwide, starting in the Americas and continuing through to November 13, 2026.
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