A widespread Microsoft 365 outage that started Thursday persisted into Friday, disrupting Outlook email access and Teams calendar features for organizations globally.
Microsoft reported that a process handling secure connections became overloaded, causing affected servers to stop processing requests. In a 7:25 am UTC update Friday, the company said a patch had improved stability on some servers and that it was working to deploy the fix more widely, though no restoration timeline was provided.
The company attempted to restore services by restarting infrastructure, redirecting network traffic, and expanding server capacity. Microsoft said there was no indication of a security breach.
Beyond email and scheduling, the outage affected Microsoft Copilot and Defender for Office 365. In Teams, users experienced trouble scheduling meetings and sending invitations, though most Teams calls and chats continued to function. The disruption also impacted third-party applications relying on Microsoft 365 services.
OpenAI reported errors in ChatGPT's Microsoft 365 connector, while Anthropic said the outage caused most email, calendar, and search requests through Claude's Microsoft 365 connector to fail.
The outage had significant impacts on government operations. 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 reported being unable to receive email Friday, and Singapore's Government Technology Agency reported that government email was among affected systems.
Microsoft 365 serves more than 450 million paid commercial seats globally, according to an October company filing. Exchange Online hosts the mailboxes and calendars used by these organizations, and outside applications depend on the same service to access that data when users connect their work accounts.
