Microsoft blames failed server health checks—not hackers—for global outage

Shortly after detecting the outage, Microsoft confirmed that the main issue was “a portion of infrastructure” that “is experiencing elevated load across multiple regions.” This was not caused by increased traffic, Microsoft said, but “a problem that’s causing servers to fail automated health checks and become unavailable.”

Once it became clear that the failed health checks were to blame, Microsoft said it took steps to prevent additional server outages while validating alternate health check methods. But four hours later, the company admitted that it was still in the weeds.

“We’re opening all available pathways to restore service, as our actions taken thus far have not provided the anticipated relief,” Microsoft said. “We found a core process on affected servers is becoming overwhelmed, causing capacity loss. To validate a potential recovery, we’re isolating a portion of infrastructure, restarting affected components, and reintroducing traffic to confirm the services remain stable before applying the change more broadly.”

Even small wins seemed to turn into new setbacks. As Microsoft worked to resolve the issue, some of the servers it brought back online would “become unresponsive again once they receive traffic,” giving the company yet another problem to solve.

Realizing that no quick solutions were coming, Microsoft moved to extend email timeout to 48 hours. As “encouraging” recovery efforts remained ongoing, Microsoft advised users that “some intermittent issues may continue” when traffic is restored.

Users upset by Copilot, Outlook issues

Microsoft’s most recent updates confirmed that it’s seeing “broader improvements in North America, sustained improvements across much of Europe, and encouraging recovery signals in Asia Pacific.”

“Some users may still experience intermittent access issues or delayed email delivery as mitigation continues across remaining affected infrastructure,” Microsoft said. “Our focus remains on stabilizing recovered infrastructure, completing mitigation in remaining impacted areas, and reducing delayed email queues and backlogs while we validate service consistency across connection methods.”

DownDetector, which tracks user reports of service issues globally, showed that connectivity losses peaked Thursday afternoon and dropped off substantially by Friday morning.

In comments, an Outlook user described the pains of monitoring email recovery, complaining that outgoing messages seem to send fine but incoming messages are received inconsistently. Some Copilot users seemed distressed that access wasn’t restored as quickly as Outlook. One Microsoft 365 user pondered, “How many offices had people with practically nothing to do? How much has this cost?”