Microsoft’s cloud infrastructure suffered a widespread outage on November 12, disrupting access to Outlook and other Microsoft 365 services, including Teams and Copilot. The company said some servers had unexpectedly become unavailable, putting extra pressure on the systems still running.

Microsoft initially reported problems connecting to Exchange Online mailboxes through different methods in the Americas, and warned that users in any region could be affected. Users reported trouble accessing mailboxes, sending and receiving email and connecting to other services. Reports also described timeouts, problems with video calls and delays in cloud file syncing.

Downdetector figures reported by Extra.ec showed more than 130,000 reports about Outlook, nearly 50,000 about Microsoft 365, more than 26,000 about Teams and about 2,000 about Copilot. These are user reports to a monitoring platform, not a verified count of people affected.

Microsoft points to unavailable servers

Microsoft said the high load on its remaining infrastructure was not caused by an increase in user traffic. Instead, some servers had unexpectedly become unavailable, adding pressure to the systems still operating. The company’s updates did not specify why those servers went offline.

To address the disruption, Microsoft said it had suspended deployments, redirected traffic away from affected infrastructure and restarted servers. At about 19:50 GMT, it said it was testing a new configuration and had restarted all affected servers.

The incidents were listed for administrators under the codes EX1550543, for Exchange Online, and MO1550821, for Microsoft 365. In an update at 22:11 UTC, Microsoft’s status panel still showed degraded service for its Business and Enterprise versions. The reports available that evening did not confirm a full worldwide recovery.

Effects reached connected services

The disruption also affected integrations that rely on Microsoft services. OpenAI said it was investigating problems that blocked new connections to its Microsoft integrations and caused malfunctions. Anthropic said an issue in an external provider’s infrastructure was reducing the performance of its Microsoft 365 connector.

Microsoft had reported a separate Teams incident in North America earlier in the day, from 9:45 to 10:53 a.m. ET, and said that issue was resolved. The later outage was broader, affecting connectivity to Microsoft 365 in multiple regions. Microsoft did not say when all affected services would return to normal.