Microsoft 365 Outage Locks Users Out of Outlook as Server Failures Spread

Microsoft 365 suffered one of its biggest outages of the year on Thursday, November 12, 2026, leaving users around the world unable to open their email, join meetings or reach the company's Copilot assistant. Outlook bore the brunt of the disruption, with outage tracker Downdetector logging more than 130,000 problem reports for the email service at the peak, shortly after 1 p.m. Eastern Time.

The trouble began shortly after noon Eastern, when users started reporting that Outlook would not load, mailboxes would not open and messages would not send. Microsoft first acknowledged problems reaching Exchange Online mailboxes in the Americas, then confirmed that users in any region could be affected. By the afternoon, the outage had become a global one, with reports coming in from North America, Europe, Asia and the Middle East, including Singapore, where Outlook reports were still climbing on Friday morning.

For many businesses, the timing could hardly have been worse. The outage struck in the middle of the American working day, taking down the tools companies rely on most: email, chat, document sharing and the AI assistant Microsoft has spent the past two years putting at the centre of its workplace software.

What went down, and how big it was

Microsoft's service health alert named five services as potentially affected: Exchange Online, Microsoft Teams, SharePoint Online, Microsoft 365 Copilot and Microsoft Defender XDR. In practice, the disruption reached further. Users also reported problems with OneDrive and with Word, Excel and PowerPoint online, and Microsoft's own status page was briefly unreachable at one point.

Downdetector, which counts user-submitted reports rather than the number of people affected, recorded more than 130,000 Outlook reports at 1:27 p.m. ET. Microsoft 365 as a whole drew more than 46,000 reports, and Teams around 3,000. By 4:30 p.m. ET, Outlook reports had fallen to about 50,000, still far above normal, while Microsoft 365 reports remained above 38,000. In Singapore, the tracker recorded 250 Outlook reports at 7:05 a.m. on Friday, more than doubling to 535 by 7:55 a.m. local time, a sign the incident was still being felt in Asia well into the next day.

Microsoft had already had a difficult day before the main outage. Earlier on Thursday, the company fixed a separate Teams disruption affecting users in North America, an incident it said had been fully resolved.

Servers failed their health checks

Microsoft first described the problem as elevated load across multiple regions. As the afternoon went on, it gave a clearer account: a large number of its own servers had become unexpectedly unavailable after failing automated health checks, and an overloaded core process was causing some servers to stop responding. The extra load was not caused by more traffic, the company said, and nothing in its updates points to an attack. The failure was inside Microsoft's own infrastructure, and the load it created cascaded onto the servers that were still running.

The company paused all deployments and configuration changes, moved traffic off the affected infrastructure and began restarting the affected servers one by one, in an isolated manner, so that a server brought back online would not immediately be overwhelmed again. By around 4 p.m. ET, Microsoft said it had validated an alternative health-check method that had brought some affected servers back online. At around 6 p.m. ET, it reported limited recovery, with a portion of the affected servers returning to service, and warned that restoration would be gradual as clients reconnected.

Microsoft is tracking the incident under the codes EX1550543 and MO1550821 in the Microsoft 365 admin centre, and administrators can follow updates at the company's service status page.

The outage spread beyond Microsoft

The disruption also reached other companies that depend on Microsoft's cloud. OpenAI and Anthropic both reported problems with their Microsoft connectors, the links that let their AI services read users' email and calendars. Anthropic said most email and calendar queries and search were still failing late on Thursday evening.

As of Friday morning, Microsoft was still working to restore the affected infrastructure. Some servers had come back and stayed stable, but the company had not confirmed full recovery and had not published a root cause. The incident was still listed as ongoing in the early hours of Friday in Asia, where reports were still rising.

Why it matters

The outage is a reminder of how much of the working world now runs on a handful of cloud platforms. When Outlook goes down, it is not one company's problem: email, calendars, documents and meetings stop together, and the companies that build on top of Microsoft's services feel it too. For Microsoft, the incident also lands at an awkward moment, as it pushes customers to trust Copilot and its cloud with ever more of their daily work.

Note: the photo above shows Microsoft's campus in Redmond, Washington. It is a related image of the company, not a picture of the outage itself.

Sources

• Reuters — Microsoft 365, Outlook down for thousands of US users, Downdetector shows
• Outlook India — Microsoft Outage: Outlook, Teams And Copilot Disrupted Worldwide
• Channel News Asia — Singapore users affected in global Microsoft outage with Outlook, Teams down
• Interesting Engineering — Microsoft outage affects 130,000 users as server failures spread
• CNBC TV18 — Microsoft Down: Outage impacts Outlook and other 365 services
• Spider Designers — Microsoft 365 Outage Nov 2026: What UAE Businesses Need to Know
• AsiaOne — Is Outlook down? Widespread outage hits Microsoft email and other apps
• Pivot News — Microsoft 365 outage hit Outlook, Teams and Copilot