A Microsoft outage disrupted Outlook, Teams and Copilot, also breaking OpenAI and Anthropic connectors to Microsoft 365 accounts.
Microsoft 365, Outlook and Teams went down for thousands of US users on Thursday, November 12. Reuters reported that the disruption also hit the connectors OpenAI’s and Anthropic’s AI services use to reach Microsoft accounts.
“Microsoft 365, Outlook and Teams were down for thousands of US users on Thursday, according to outage-tracking website Downdetector.com, with the disruption also hitting connectors used by OpenAI’s and Anthropic’s AI services.” Reuters states
Downdetector, which collates status reports from several sources, logged more than 97,000 Outlook incidents at 2:07 p.m. ET. It also recorded more than 38,000 reports of Microsoft 365 problems and about 4,500 for Teams. Reuters notes the number of affected users may vary. Expers observed complaints surge that afternoon across Outlook, Microsoft 365, Teams, Copilot, Azure, OneDrive and the Microsoft Store.
In a Microsoft 365 admin center notice (MO1550821), Microsoft warned that users might have trouble accessing several services, including Exchange Online, Teams, SharePoint Online, Microsoft 365 Copilot and Microsoft Defender XDR.
Microsoft said the outage started at 1:26 p.m. ET. However, it had already been investigating problems connecting to Exchange Online mailboxes in the Americas earlier that day. The company later confirmed that users worldwide could be affected.
Microsoft initially blamed heavy workloads across several regions. However, it later found that increased traffic was not the cause. In an update on X, the company said it was working to safely bring several unavailable servers back online. Their loss was putting extra pressure on the remaining infrastructure.
Its response so far has been to pause all deployments, redistribute connection traffic across its worldwide infrastructure and move additional traffic away from affected systems. It’s also restarting the affected servers to restore capacity. In a statement to Reuters, Microsoft said it was aggressively pursuing all pathways to reduce impact.
“We’re aggressively pursuing all pathways to reduce impact,” states Microsoft.
“We determined the elevated load isn’t driven by an increase in traffic, but by a number of servers being unexpectedly unavailable; straining the remaining infrastructure. We’re working to safely return them to service,” Microsoft wrote on X.
Microsoft first blamed the disruption on high infrastructure demand across several regions. However, it later found that the issue was caused by servers unexpectedly going offline.
Microsoft also reported a separate Teams outage (TM1550488) that affected users in North and South America from 9:45 to 10:53 a.m. ET. Users experienced delays or failures when sending messages, creating or updating conversations, and retrieving chat messages. Microsoft traced the problem to resource contention within its infrastructure, which increased resource usage and prevented Teams from processing messages properly. The company confirmed that the issue has been resolved.
At this time the massive outage has yet to be resolved. Reuters says Microsoft later told customers the issue may also affect Microsoft 365 connectivity for users in other regions.
The impact also extended to AI services. OpenAI reported problems with its Microsoft connectors, saying new connections might fail and tools might not work properly. Anthropic also reported an issue with its Microsoft 365 connector caused by a problem at an upstream provider. As a result, Copilot and competing AI services were unable to access users’ inboxes because the underlying Microsoft services were unavailable.
IT teams should check the Microsoft 365 admin center for updates rather than make assumptions about the cause. They should also expect emails and messages to be delayed until services fully recover.
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Source: Security Affairs · 2026-11-12