Microsoft 365 outage hits Outlook, Teams and AI connectors as patch widens
In brief
- Microsoft 365's global outage began Thursday and ran into Friday, disrupting Outlook and some Teams features.
- Microsoft blamed an overloaded secure-connection process and said there was no indication of a breach.
- ChatGPT and Claude's Microsoft 365 connectors failed, according to OpenAI and Anthropic.
- A US appeals court clerk's office, Japan's Finance Ministry and Singapore's GovTech reported email disruption.
- Microsoft's status update gave no timetable for full restoration.
What Microsoft said
In a 7:25 am UTC status update, Microsoft said 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.
Microsoft said a process that handles secure connections became overloaded, which caused affected servers to stop processing requests. It said it tried to restore services by restarting infrastructure, redirecting network traffic and expanding server capacity.
Microsoft said there was no indication of a security breach.
The damage wasn't limited to email. Some users couldn't access their Exchange Online mailboxes, and Teams users had trouble scheduling meetings and sending invitations, though Microsoft said most Teams calls and chats kept working. Features in Microsoft Copilot and Defender for Office 365 were affected as well.
Why ChatGPT and Claude broke too
So why would an email outage hit AI assistants? Exchange Online hosts the mailboxes and calendars organizations use, and outside apps (AI assistants included) rely on it to retrieve that data when users connect their work accounts.
That's where the AI tools ran into trouble. 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.
Government email disrupted
The US Court of Appeals for the Tenth Circuit said its clerk's office couldn't send or receive email for much of Thursday. Japan's Finance Ministry said it couldn't receive email on Friday. Singapore's Government Technology Agency told CNA that government email was one of the affected systems.
The footprint here is big. Microsoft reported more than 450 million paid commercial seats for Microsoft 365 in an October filing, and its latest update didn't say when service would be fully back.
Frequently asked questions
What caused the Microsoft 365 outage?
Microsoft said a process that handles secure connections became overloaded, which caused affected servers to stop processing requests. It said it tried restarting infrastructure, redirecting network traffic and expanding server capacity, and said there was no indication of a security breach.
Why did ChatGPT and Claude's Microsoft 365 connectors fail during the outage?
Exchange Online hosts the mailboxes and calendars organizations use, and outside apps, including AI assistants, rely on it to retrieve that data. OpenAI reported errors in ChatGPT's Microsoft 365 connector, and Anthropic said most email, calendar and search requests through Claude's connector failed.
When will Microsoft 365 be fully restored?
Microsoft hasn't given a timetable. In a 7:25 am UTC update, it said a patch had improved stability on some servers and that it was working to deploy the fix more widely.
