Outlook, Teams, OneDrive, Copilot and other Microsoft services are down worldwide, the company said. Businesses and ordinary users cannot get to their email.
SharePoint and the web versions of Office apps are also having problems. Defender XDR, Microsoft's security system, is affected too, which adds to the impact of the outage.
The problem at first hit only the US, but it quickly spread to "all regions".
Microsoft said on X that part of its infrastructure is carrying "high traffic volume". In a later update, it said "a large number of servers unexpectedly became unavailable", but did not give the exact causes.
Microsoft says the outage is not a cyberattack. It is investigating and rerouting connections through its global infrastructure to spread the load. The company wants to restore the services as soon as possible.
It is not Microsoft's first big problem this year. In September 2026, Microsoft 365, the company's online productivity suite, was down for several days. Official statements at the time blamed a "faulty authentication configuration".