Microsoft says a technical issue during a network capacity upgrade caused the outage affecting Outlook, Teams and Copilot across at least 74 countries, with services gradually being restored.
A major Microsoft outage has disrupted Outlook, Teams, Copilot and other Microsoft 365 services for users around the world, with problems first reported on Thursday evening and continuing into Friday.
Microsoft said the outage was caused by a technical issue during an earlier network capacity upgrade, and that it was not a cyber-security incident. The company said it had addressed the underlying issue and was restoring service gradually.
"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," Microsoft said.
Problems were reported in at least 74 countries. More than 430 million people use Microsoft 365 apps according to Microsoft's website, though the full scale of the outage has not been confirmed.
Users reported being unable to send or receive emails, view files, or access calendar details. Some users were able to use Teams messaging and online meeting functions without issues.
In the UK, NHS GP practices, pharmacies, police forces and schools were affected. The GMB union said the outage was preventing 111 and 999 services from referring patient details as they normally would, creating a "massive backlog", though emergency and life-threatening call-outs appeared to be unaffected.
The NHS urged patients to attend appointments unless told otherwise, and to use 999 in an emergency and otherwise contact 111, use NHS 111 online or visit their local pharmacy.
The government of Japan said its shared IT platform had been disrupted. Courts from Los Angeles to Texas warned that communications might be delayed. In Canada, a healthcare network running several hospitals in Toronto experienced email issues, though patient care was not affected.
OpenAI and Anthropic both reported problems linked to the outage. OpenAI said it was investigating an issue with Microsoft connectors where new connections may be broken and tools were not working as expected. Anthropic said Claude's mail, calendar and search tools in the Microsoft 365 connector were still failing for most requests, and that Claude for Outlook remained affected.
Microsoft said it was seeing "encouraging recovery progress" in Europe and improvement in North America, with email queues significantly reduced and approaching normal levels. The company warned some users may still experience intermittent access issues or delayed email delivery.
Microsoft extended the "timeout window" to 48 hours to help protect delayed messages as delivery catches up. When delayed emails arrive, the timestamp will be when they were delivered rather than when they were sent.
The outage has lasted more than 20 hours, which is considered a long time for an outage. Experts said the challenge is not just fixing the fault but managing the huge surge of devices trying to reconnect once services come back online. Microsoft said it would provide a full post-incident report once its review is complete.
Sources
This article was drafted with AI assistance and checked against the sources above. Company claims are reported as claims. Cover image is AI-generated.
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The Federal Aviation Administration lifted a nationwide ground stop caused by communications problems, allowing airplane departures to resume after roughly four hours.
Microsoft apologized for a widespread outage that disrupted Outlook, Teams and other Microsoft 365 services, saying it addressed the underlying issue and detected no malicious activity.
