Microsoft restores Microsoft 365 after global outage, says no cyberattack
In brief
- Microsoft 365 services are restored after an outage lasting more than 24 hours, Microsoft said.
- Microsoft traced the problem to a previous network capacity upgrade.
- Cyber activity and AI agents were not behind the issue, according to Microsoft.
- OpenAI and Anthropic reported their Microsoft 365 connectors working again.
- A full post-incident report will follow Microsoft's review, the company said.
What broke, and why
The outage began on Thursday. It cut off access to Exchange Online mailboxes and to features tied to Outlook, Teams and Microsoft Copilot, Cointelegraph reported.
On Friday, Microsoft said the outage came from a problem introduced during a previous network capacity upgrade (the issue showed up after a recent network change). The company was also direct about what it wasn't.
“This was a technical issue not related to cyber or AI/agents,” the company said.
That's the only explanation on the record so far.
Microsoft said it fixed the underlying issue and brought services back gradually, checking stability before it moved on to each next stage. By Saturday, the company said it had restored service to the remaining affected customers and regions, and it pointed customers to incident MO1550821 in the Microsoft 365 admin center.
Governments and AI apps were hit too
The disruption reached past corporate inboxes. Government agencies in Japan, Singapore and the United States had email problems during the outage, according to Cointelegraph.
Connections between Microsoft 365 and AI assistants were affected as well. It's a reminder of how many apps now sit on top of the same mail and calendar plumbing. OpenAI said the Microsoft 365 connector in ChatGPT was working normally again, while Anthropic marked its Microsoft 365 connector and Claude for Outlook incident as resolved.
The full report is still to come
Microsoft apologized for the disruption. It said it'll publish a full post-incident report once its review is complete, and until that report lands, the network capacity upgrade is the cause Microsoft has given (nothing more detailed has been published yet).
Admins who want the official record of what happened can follow incident MO1550821, which is where Microsoft has been directing customers. We'll see what the post-incident report adds once it's out.
Frequently asked questions
What caused the Microsoft 365 outage?
Microsoft said the outage came from a problem introduced during a previous network capacity upgrade, which surfaced after a recent network change. The company said it will publish a full post-incident report once its review is complete.
Was the Microsoft 365 outage a cyberattack?
No, according to Microsoft. The company repeated that the disruption was not caused by a cyberattack and said it was a technical issue not related to cyber activity or AI agents.
Were ChatGPT and Claude integrations affected by the Microsoft outage?
Connections between Microsoft 365 and AI assistants were affected. OpenAI said the Microsoft 365 connector in ChatGPT was working normally again, and Anthropic marked its Microsoft 365 connector and Claude for Outlook incident as resolved.
