Microsoft is struggling to restore many of its cloud services after a core process running on some servers became “overwhelmed” and its attempts to fix the problem failed.
The incident started at around 18:00 UTC on November 12, and meant services including Exchange Online, Teams, Copilot 365, and Defender for Office 365 became unavailable. Admins trying to figure out what was wrong couldn’t access tools like Intune or the Microsoft 365 Apps Admin Center – they went down, too.
On its X feed, Microsoft blamed “a problem that's causing servers to fail automated health checks and become unavailable.”
The company said it hasn’t spotted any changes to its systems that might have sparked the incident, but its early investigation “indicates the failed health checks may originate from a specific component that's responsible for processing server health.”
The company’s status page offers contradictory information, saying Microsoft’s people are “assessing whether reverting the small number of recent configuration updates we identified could help accelerate recovery.”
According to a Xeet published at around 22:00 UTC, Microsoft said it found and validated an alternative service health check method, “which allowed a subset of affected servers to successfully return to service.”
“We're continuing to work through restarting and validating the affected servers to safely return them to service, and we're exploring opportunities to expedite this process,” the company wrote.
But those efforts may not be working.
“We’re continuing to pursue all available pathways to restore service, as our actions taken thus far have not provided the anticipated relief,” the status page advises. “Our investigation has found that a core process on the affected servers is becoming overwhelmed, which causes the servers to stop responding and contributes to the capacity loss.”
The incident means email is not flowing for many Microsoft customers: friends and family of writers tell us their working days are severely disrupted.
Microsoft’s most recent Xeet on the matter, published about an hour before this story went live, says it's trying to validate a potential recovery by “isolating a portion of infrastructure, restarting affected components, and reintroducing traffic to confirm the services remain stable before applying the change more broadly.”
But the software giant hasn’t offered any timeline for full service restoration.
This is a developing situation and will update this story as more information becomes available. ®
to add news that Microsoft says it has brought some servers back online and that they "initially remain healthy" but "can become unresponsive again once they begin receiving traffic."
So not usefully healthy at all, then.
"We're analyzing diagnostic data from these servers with our networking and platform experts to determine what's triggering this behavior," the company advised.