Business · Companies

Microsoft 365 Outage Lasting Over 24 Hours Drew 7.4 Million Reports

A Microsoft 365 outage that knocked out Outlook and Teams for more than 24 hours drew 7.4 million reports on Downdetector. Microsoft says services are fully restored, and insurers estimate global insured losses of up to US$500 million.

By matthew jonathan

November 15, 20263 min read

Microsoft 365 Outage Lasting Over 24 Hours Drew 7.4 Million Reports

A Microsoft 365 outage that lasted more than 24 hours generated nearly 20,000 complaints a minute at its peak, according to Downdetector, the outage-tracking site. Microsoft said services have now fully recovered across Teams, Outlook, Copilot and other applications.

Downdetector logged more than 7.4 million reports worldwide. The peak was more than 1,500 times normal levels.

How big the outage was

Reports reached 74 countries and territories within about an hour. Downdetector recorded 19,650 reports a minute across five Microsoft services at the peak, against fewer than 15 on a typical day. Outlook alone drew nearly 130,000 reports in the United States.

Those figures are user-submitted complaints, not a count of people affected. Microsoft had more than 450 million paid user licenses as of January 2026, according to its financial reporting.

People could not send emails, manage calendars or host virtual meetings. Microsoft said the disruption began at 11:17 a.m. ET and first hit Exchange Online, the cloud email service behind Outlook.

What Microsoft says went wrong

Microsoft first suspected unusually heavy traffic was overwhelming part of its infrastructure. Further checks showed several servers had unexpectedly become unavailable, which put more pressure on the rest.

Engineers restarted servers and rerouted traffic, but some stopped responding again once connections resumed. Microsoft then patched an authentication and routing component, which it said produced encouraging results.

Tech expert Val Quinn said a core process on the affected servers had become "overwhelmed", and automated health checks then shut them down. Turning them back on was not simple, he said. A huge backlog of emails and messages had queued up, and loading it all at once risked new problems.

Microsoft has found no sign of malicious activity and has not yet confirmed the underlying cause. It plans a detailed report once the incident is resolved.

Governments and businesses hit

Japan confirmed problems with communications between ministries. Chief Cabinet Secretary Minoru Kihara said several services, including Outlook, had become unavailable, though he reported no problems with medical care or electronic patient records.

Australia's federal police and intelligence agency were affected. Home Affairs Minister Tony Burke said he had spoken with Microsoft's regional leadership. He said Microsoft did not believe a cyberattack caused the outage.

A financial company in Taiwan used fax machines to confirm trades. Another cancelled a bond repurchase deal. Euronext had email problems affecting its listing teams, British insurer Aviva prepared backup arrangements for its earnings calls, and Danish shipping company Maersk warned customers of possible delays.

The cost

Mario De Cicco, vice president of European financial institutions at Morningstar DBRS, estimated global insured losses at between US$300 million and US$500 million. He expects the overall hit to insurers to be limited.

RMIT Associate Professor Mark Gregory said the lost productivity would run to tens of millions of dollars in Australia and tens of billions globally. He urged people to keep a backup email account, such as Gmail, and businesses to back up billing and accounting systems.

"Unfortunately, I see many businesses that are not prepared to look at having that redundancy or backup approaches," Gregory said. Microsoft also had 365 outages in January this year and October last year, and an Azure cloud outage last month.