Microsoft 365 outage knocked out email, Teams and hospital systems for a day
A single technical glitch inside Microsoft's network took down Outlook, Teams and Copilot across 70+ countries, disrupting hospitals, police, airlines and governments for roughly 24 hours.
What happened: Just after noon ET on a Thursday, Outlook users started flooding Downdetector with outage reports. Microsoft confirmed it was investigating a problem that initially looked confined to North America, but within an hour it had spread to more than 70 countries, knocking out Outlook, Teams, Copilot and other Microsoft 365 services for tens of millions of businesses, governments and individuals. It took roughly 24 hours before Microsoft's status page showed broad recovery.
Why it matters: This wasn't just inconvenienced office workers. Governments in Japan and the US reported disrupted functions, airlines struggled to reach customers, law enforcement and emergency services were affected, and hospitals reported widespread interruptions to their operations. When one company's cloud quietly underpins email, scheduling and communication tools across so many critical services at once, a single internal fault becomes everyone's emergency at the same time.
How it works, plainly: Microsoft repeatedly ruled out a cyberattack and said AI or AI agents played no role. Instead, the company traced the failure to an issue introduced during an earlier network capacity upgrade that resurfaced after a subsequent network change, ordinary infrastructure maintenance gone wrong, not an attack or an algorithm acting on its own. Microsoft says it fixed the underlying issue but has not yet published the full post-incident report explaining exactly how it happened.
The rollout: As systems came back online, Microsoft extended its email delivery queue to 48 hours so that nothing sent during the blackout would be lost, which means users are now bracing for a delayed flood of backed-up messages and notifications. Microsoft says it will publish a full post-incident report once its review is complete, but for now the precise root cause and full scope of real-world harm, especially to emergency and medical services, remain undisclosed.