Microsoft outage knocked out Outlook and Teams for 130,000 users

Nearly 130,000 users worldwide reported failures across Microsoft 365 on Thursday, hitting Outlook, Teams, Word, Excel, PowerPoint, SharePoint, OneDrive and the Copilot AI assistant before Microsoft began bringing servers back online.

Outage tracker Down Detector logged the spike in reports. Users said they couldn't send or receive email, and some couldn't load their inboxes at all. New reports fell from the peak as the evening wore on, but connectivity complaints persisted.

Microsoft first flagged the problem on X, saying it was "investigating reports of users experiencing issues accessing Exchange Online mailboxes through multiple connection methods." The company then explained that part of its infrastructure was "experiencing elevated load," which it called "likely contributing to the connectivity errors."

What actually broke?

The root cause wasn't a traffic surge. Microsoft said it had "determined that the elevated load isn't driven by an overall increase in traffic, but by a large number of servers being unexpectedly unavailable, which is shifting load onto the remaining infrastructure." Those servers failed during automated checks, knocking them out of rotation and squeezing capacity onto whatever remained.

The company's review of recent changes has identified configuration updates as a potential cause. That lead is still under investigation.

How did Microsoft fix it?

By 9pm UTC Thursday, Microsoft said it had validated an alternative health check method on a subset of the affected servers. That method let them successfully return to service, and the fix was being applied more broadly across the estate. Microsoft was also building an automated process to detect and restart unresponsive servers without manual intervention.

An earlier service degradation alert on the company's status site said it was "aggressively pursuing all pathways to reduce impact" and "restarting affected servers to return them to service."

As a defensive measure, Microsoft froze its release pipeline. "As a precaution, we've paused all deployments and configuration changes while we review recent changes for any correlation to this event," the company said. "We're investigating what's causing these servers to become unavailable while we work to safely return them to service."

Was Teams hit too?

Yes, and unevenly. Microsoft said earlier that it had "successfully restored" the Teams problems in North America, though some users kept reporting connection issues after that announcement. The company didn't say when full global restoration is expected.

Why does it matter for business?

The outage shows how much of the working world runs on a single vendor's infrastructure. When Microsoft's automated health checks misfire, email, chat, file storage and document editing fail at once, across continents, for enterprises that pay for uptime. The suspected culprit — configuration updates — sits inside Microsoft's own deployment pipeline, meaning the failure came from routine internal change, not external attack or traffic spikes.

Microsoft has pinned its near-term credibility on the restart automation it's now preparing and on the broader rollout of the validated health check fix. A post-incident root-cause report, and whether the deployment freeze holds, will show whether Thursday's 130,000 reports were a one-off or a warning about how much automated infrastructure change can cost when it goes wrong.