Microsoft 365 users across the United States, including Alaska, faced connectivity errors Thursday as the company worked to resolve a widespread outage tied to unusually heavy strain on parts of its server infrastructure.
According to an alert posted to the Microsoft Admin Center, the problem was not caused by a surge in traffic. Instead, the company said a number of servers became “unexpectedly unavailable,” putting added strain on the systems still running.
“We’ve determined a portion of infrastructure is experiencing elevated load across multiple regions, which is likely contributing to the connectivity errors,” Microsoft said, pointing users to incident reports EX1550543 and MO1550821 in the admin center for further detail.
Microsoft has not said why the affected servers went offline. The company’s statement that traffic volume was not to blame appears to rule out a denial-of-service attack, though officials have not ruled out other possible causes. As of this writing, the company’s public focus has been on restoring service rather than explaining the root cause.
“We’re working to safely return them to service,” Microsoft said, adding that it was “aggressively pursuing all pathways to reduce impact.”
Which services were affected
The outage touched a range of widely used Microsoft products, including Exchange Online, Microsoft Teams, SharePoint Online, Microsoft Copilot 365 and Microsoft Defender XDR. Thousands of users attempting to reach their email through Microsoft 365 were affected.
“We’re investigating reports of users experiencing issues accessing Exchange Online mailboxes through multiple connection methods in the Americas,” the company said in a separate alert.
The outage-tracking site “Is It Down Right Now?” showed problems extending beyond Microsoft’s own products, with reported issues at Cloudflare, Elastic Cloud, Sentry, OpenAI, Anthropic, Twilio and HubSpot, along with difficulties affecting Xbox and Amazon.
Fix underway
Microsoft said its engineers identified the source of the disruption and have begun shifting traffic away from the strained infrastructure.
“We’ve begun redistributing connection traffic across our broader worldwide infrastructure to help balance the load. We’ve paused all deployments, we’re moving additional traffic off the affected infrastructure, and we’re restarting affected servers to return them to service.”
Microsoft has not yet given a timeline for full restoration of all services.
