Microsoft began restoring Outlook, Teams and Copilot on Friday after a global outage that lasted nearly 18 hours, left millions of users without access and reached at least 74 countries.
Problem reports came in from 74 countries and territories within about an hour of the first failures on Thursday, November 12. Reports across five Microsoft services peaked at 19,650 per minute, compared with fewer than 15 on a typical Thursday. In the United States, Outlook reports reached about 130,000 at their height.
Businesses, schools, medical facilities and some transport services were disrupted. Government systems were also affected. Singapore’s Government Technology Agency said government emails were down, and the U.S. House of Representatives said its engineers were working with Microsoft.
Microsoft 365 connectors used by OpenAI and Anthropic also had problems. Some users could not log in to other services because they could not receive two-factor codes by email.
Microsoft said it found no sign of a cyberattack. The company said “a process on the affected servers responsible for establishing secure connections becomes overwhelmed.” When that happens, the servers stop processing requests. Overall traffic had not increased. Servers returned to service repeatedly became unresponsive again once user traffic reached them.
The company began reversing a recent network configuration change that coincided with the start of the outage. It has not confirmed that the change was the root cause. Executive Vice President Charles Lamanna said there is no indication the outage resulted from malicious activity.
On Friday, Microsoft said it was seeing “early stabilization and capacity improvements,” though some intermittent issues may continue. It also extended its email timeout window to 48 hours to help protect delayed messages.
This is not the first large Microsoft 365 disruption this year. An outage in January left North American users without service for almost 10 hours. Microsoft has promised a post-incident report once the current disruption is contained.
