Microsoft 365 outage disrupts Outlook, Teams and Defender XDR portal for many tenants

On November 12 and 13, 2026, Microsoft 365 suffered one of its largest outages of the year, leaving Outlook, Teams, SharePoint Online, Copilot and the Defender XDR portal degraded or unreachable for many organizations. The disruption began around 1:26 PM Eastern time on November 12, initially appearing as Exchange Online mailbox problems in the Americas before spreading to all regions. Microsoft attributed it to an overwhelmed process that establishes secure connections, which caused servers to fail automated health checks, and reported no evidence of a cyberattack. Recovery steps included pausing deployments, redistributing traffic, restarting servers and rolling back a recent network configuration change, with gradual recovery reported by late evening US time. The root cause had not been confirmed at the time of publication.