Microsoft Says Fault in Capacity Update Caused Global Microsoft 365 Outage

Overview

• A multi‑hour outage that began on Nov. 12 knocked Outlook, Teams, Copilot and other Microsoft 365 services offline for users in more than 70 countries and generated tens to hundreds of thousands of incident reports.
• Microsoft traced the failure to servers that became unexpectedly unavailable after a prior capacity or network update and says it has identified and corrected the principal fault.
• The company says services are being restored gradually with measures that included suspending updates, redirecting traffic away from affected infrastructure and restarting problem servers.
• To limit lost mail the firm extended delivery retry windows to 48 hours and warned some users may still see intermittent access problems and delayed queues while remaining infrastructure is mitigated.
• The outage disrupted hospitals, government offices, financial firms and airlines and highlights wider risks from heavy reliance on a single cloud provider; Microsoft plans a formal post‑incident report on causes and safeguards.