Microsoft 365 outage pushes banks and traders back to faxes and phones
In brief
- Microsoft 365 disruption began around midday Eastern Time on November 12, according to Crypto Briefing.
- Exchange Online, which powers Outlook email, was hardest hit; Teams, SharePoint and OneDrive also degraded.
- Downdetector logged peak issue reports above 130,000 for Outlook alone.
- Microsoft blamed servers failing automated health checks under elevated loads, not a cyberattack or AI.
What broke
Exchange Online (the backend that powers Outlook email) took the hardest hit, according to Crypto Briefing. Mailboxes were delayed or couldn't be opened at all. Teams, Copilot, SharePoint, OneDrive and Defender XDR also ran into connectivity problems or degraded performance.
Downdetector logged peak issue reports above 130,000 for Outlook alone. Crypto Briefing said the outage reached users in at least 74 countries and territories. Microsoft hasn't given a total count of affected users. Its 365 suite has an estimated user base of over 430 million globally (that's the size of the platform, not a tally of who lost access).
Faxes on the trading desk
Trading desks in Taiwan and Japan turned to faxes to confirm trades, Crypto Briefing reported. Euronext, the European exchange operator, told listed companies to reach it by phone while it verified callers' identities. Airlines, health services and police forces were also affected, and some companies pushed back earnings releases or customer updates because they couldn't reliably get the word out.
Most institutions reported that their core systems kept running.
It was the communication layer that failed, which is why a 12-to-18-hour email problem spilled into earnings calendars and trade confirmations.
Microsoft's explanation
Microsoft traced the problem to servers failing automated health checks under elevated loads, according to Crypto Briefing. The company stressed the outage wasn't caused by a cyberattack or by problems with AI. Microsoft reported signs of stabilisation by the afternoon of November 13 after rolling out fixes more broadly, as email delivery moved back toward normal levels.
Crypto Briefing framed the episode as a concentration-risk story. Many organisations run email, messaging, document storage, security tooling and now AI assistants through one provider, the outlet wrote. In its reading, the outage shows the risk of leaning that heavily on a single vendor, and it makes the case for businesses to build contingency plans before the next disruption hits.
Frequently asked questions
What caused the Microsoft 365 outage in November?
Microsoft traced the problem to a technical issue in which servers failed automated health checks while under elevated loads, according to Crypto Briefing. The company stressed the outage wasn't caused by a cyberattack or by problems with AI.
How many people were affected by the Microsoft 365 outage?
Microsoft hasn't given a total count of affected users. Downdetector logged peak issue reports above 130,000 for Outlook alone, and Crypto Briefing said the outage reached users in at least 74 countries and territories. Microsoft 365's estimated 430 million-plus user base describes the platform, not the outage.
Which Microsoft services went down during the outage?
Exchange Online, the backend that powers Outlook email, took the hardest hit, with mailboxes delayed or impossible to open. Teams, Copilot, SharePoint, OneDrive and Defender XDR also ran into connectivity problems or degraded performance.
