Microsoft 365 services are back online after a 24-hour outage affected businesses, governments, and tens of millions of users globally.
The disruption started around noon ET on Thursday on the East Coast. Downdetector logged reports of Outlook failures shortly after 12 pm ET. Microsoft confirmed an investigation within the hour. The issue quickly expanded to impact more than 70 countries.
The exact cause remains unknown. The company repeatedly ruled out a cyberattack on its status page. It also stated that AI or AI agents played no role in the incident.
“We are seeing broad recovery and stability across our services,” a Microsoft spokesperson said. “This was a technical issue not related to cyber or AI/agents. The incident was introduced by an issue during an earlier network capacity upgrade that surfaced following a recent network change. We have addressed the underlying issue and continue to restore service to remaining customers and regions.”
The company promised a full post-incident report after a complete review of the failure.
What happens to your inbox
As Outlook, Teams, Copilot, and other Microsoft 365 systems return, users will likely face inbox clutter. Jonathan Leitschuh, an independent researcher, noted that people will probably receive many notifications when services come back.
Microsoft increased email queue times to 48 hours to ensure every message sent during the downtime gets delivered. Leitschuh warned that users may still receive a flood of notifications a few hours later as subsystems come back online.
The total impact of the outage may never be fully known, but the disruption is already significant. Governments from Japan to the United States reported problems across many functions. Airlines faced issues communicating with customers. Many law enforcement and emergency services stopped operations. Hospitals reported widespread interruptions to their work.
The episode highlights the risks of relying on a single company for critical services. “We’re very interdependent on these systems in modern life,” Leitschuh said. Next time, delayed emails may be the least of our worries.
