Microsoft 365 Outage Traced to Exchange Online Server Health Check Failures

A Microsoft 365 outage beginning November 12, 2026 degraded Exchange Online, Outlook, Teams, Copilot, SharePoint Online, Intune, and Defender across the globe, starting in the Americas. According to Microsoft's status updates, servers failed automated health checks and dropped offline, pushing extra load onto the remaining servers until they too were overwhelmed. Microsoft has said traffic volume did not increase and that it sees no sign of malicious activity, while the root trigger for the initial failures remains unidentified. Recovery was reported in North America and much of Europe by November 13, with email queues significantly reduced, though a post-incident review has not yet been published.