Microsoft 365 Outage Hits 321 Million Users as Unavailable Servers Cripple Outlook, Copilot and Teams Features
Updated
Updated · Fox Business · Nov 12
Microsoft 365 Outage Hits 321 Million Users as Unavailable Servers Cripple Outlook, Copilot and Teams Features
3 articles · Updated · Fox Business · Nov 12
Summary
Hours into Thursday’s disruption, Microsoft said a core process on affected servers was being overwhelmed, forcing it to isolate infrastructure, restart components and gradually reintroduce traffic.
Unexpected server unavailability—not a traffic surge—drove elevated system loads, and some restored servers became unresponsive again once traffic returned, prompting Microsoft to rebuild part of the fleet using a previous configuration.
More than 130,000 issues had been reported on Downdetector by 2 p.m., with Exchange Online, Outlook, Copilot, Defender, Graph, Planner, Purview and some Teams functions among the services affected.
Microsoft said core Teams messaging and online meetings remained largely functional, but email delivery, admin tools, school features and some security checks were disrupted across multiple regions.
The outage underscored how a relatively simple server-capacity failure can cascade at hyperscale, with Microsoft still unable to say how long restoration would take.