Microsoft 365 outage knocks out Outlook, Teams and Copilot worldwide for nearly a day; Microsoft blames network upgrade, rules out cyberattack

Microsoft 365 went down worldwide from Thursday afternoon (November 12), knocking out Outlook email, Teams, SharePoint and Copilot for nearly a day across 74 countries and territories. Microsoft said on Friday (November 13) that the incident was introduced during an earlier network capacity upgrade and surfaced after a more recent network change, and was not a cyberattack. The company said the underlying fault has been fixed and service is being gradually restored, though some customers and regions were still waiting and the incident had not been formally closed.

What was hit

Outlook was hit hardest: large numbers of users could not open their Exchange Online mailboxes, or saw severe mail delays. The trouble then spread to Teams, SharePoint Online, OneDrive, Microsoft 365 Copilot and Defender XDR. Outage tracker Downdetector received reports from 74 countries and territories within about an hour, totalling more than 130,000 reports. Microsoft said its Azure cloud hosting business was not itself part of the incident, although outage trackers also showed reports for Azure.

Microsoft: not an attack

Microsoft apologised on Friday, saying: “We are deeply sorry for the disruption this incident has caused our customers and partners.” The company said the outage was not a cyberattack and was not related to AI agents. Its preliminary explanation is that the problem was introduced during an earlier network capacity upgrade and only surfaced after a more recent network change. Microsoft promised a full post-incident report once service is fully restored.

A faltering recovery

The outage began at about 16:00 GMT on Thursday (11 a.m. Eastern), first in the Americas, and Microsoft opened incident references EX1550543 (Exchange Online) and MO1550821 (Microsoft 365 overall). Microsoft said a large number of its servers had unexpectedly become unavailable, and that the elevated load was not caused by a surge in traffic. Early on Friday it began rolling back a recent network change, but at one point said the changes were “not taking as expected”; by midday Friday it reported only “marginal success”.

By Friday afternoon, recovery was visible across North America and much of Europe. In an update at 17:50 UTC on Friday, Microsoft said the underlying issue had been fixed and broad recovery was under way, but it was still restoring service for the remaining customers and regions. The outage lasted nearly a full day.

Third major outage this year

It is Microsoft 365's third major outage this year: one in January lasted nearly 10 hours, and one in September lasted several days and was blamed on a core authentication configuration. The Verge, citing sources, linked this outage to configuration changes in Azure Virtual Network; Microsoft has not confirmed that account. During the outage, government departments, hospitals, airlines and businesses were disrupted, underlining the knock-on effect when the world's most widely used office cloud stops working.