Microsoft outage disrupts Outlook, Copilot and AI connectors in 70+ countries for 18+ hours

A Microsoft 365 failure that began Thursday knocked out Outlook for businesses and governments in more than 70 countries and took Microsoft's Copilot down with it. The outage also disabled Microsoft connectors used by Anthropic's Claude and OpenAI's ChatGPT to reach users' mail and calendars. Microsoft said the common dependency was Exchange Online, its cloud email and calendar backend. Teams calls and chats and files stored directly in SharePoint remained functional, while anything requiring mailbox access failed.

Microsoft's status updates said features interacting with Exchange Online were impacted, while services not dependent on mailbox interaction remained functional. The company first attributed the disruption to elevated load, then said it was not driven by increased traffic but by many servers failing automated health checks and shifting load to remaining machines. Servers brought back online sometimes became unresponsive again. Microsoft paused deployments, patched an authentication and routing component, and extended email timeouts to 48 hours.

The incident shows how tightly linked enterprise AI workflows are to legacy office plumbing. Claude, ChatGPT and Copilot depend on Microsoft Graph and Exchange Online to read mail, calendar and files, so a single backend fault can idle multiple assistants at once. Reports of traders using fax machines and Japan's finance ministry posting paper notices underscored fallbacks when cloud coordination fails. Microsoft said it saw no evidence of malicious activity and promised a full post-incident report.

Businesses and governments relying on Microsoft 365 lost access to email, scheduling and AI-assisted search, interrupting ordinary operations and automated workflows. The outage also exposed concentration risk: many firms and agencies use the same cloud provider, the same authentication and data connectors, so a fault at one point can propagate across vendors and national administrations. For customers, the immediate stakes are continuity, lost productivity and trust in AI-driven office tools.