Microsoft 365 outage hits Outlook email and Teams calendars worldwide

A global Microsoft 365 outage continued into Friday, disrupting Outlook email and some Teams features.

Microsoft said in a 7:25 am UTC update that a patch had improved stability on some servers and that it was working to deploy the fix more widely. The update, republished by the University of Pennsylvania, gave no timetable for restoration.

The outage began Thursday, leaving some users unable to access their Exchange Online mailboxes. Microsoft said a process that handles secure connection became overloaded, causing affected servers to stop processing requests.

The company said it attempted to restore services by restarting infrastructure, redirecting network traffic and expanding server capacity. Microsoft said there was no indication of a security breach.

The outage also affected features in Microsoft Copilot and Defender for Office 365. In Teams, users had trouble scheduling meetings and sending invitations. Microsoft said most Teams calls and chats continued to work.

Businesses and government agencies worldwide use Microsoft 365 for email and scheduling. Microsoft reported more than 450 million paid commercial seats for the suite in an October filing. Exchange Online hosts the mailboxes and calendars those organizations use, and outside apps, including AI assistants, rely on the same service to retrieve that data when users connect their work accounts.

OpenAI reported errors in ChatGPT’s Microsoft 365 connector. Anthropic said the outage caused most email, calendar and search requests through Calude’s Microsoft 365 connector to fail.

The US Court of Appeals for the Tenth Circuit said its clerk’s office could neither send nor receive email for much of Thursday. Japan’s Finance Ministry said it was unable to receive email on Friday and Singapore’s Government Technology Agency told CNA that government email was among systems affected.

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