Microsoft Outlook goes dark worldwide

Outlook goes down across the world

At about eight pm, Microsoft acknowledged that people in the Americas could not reach their Exchange Online mailboxes. Soon after, it said users in any region could be affected.

Complaints peak above 138,000

By Downdetector's count, Outlook complaints peaked above 138,000 around the time Microsoft conceded the outage was global. The disruption was still running when Microsoft issued its latest update.

Microsoft's first theory: server overload

Microsoft initially said part of its infrastructure was straining under load. It paused deployments, rerouted traffic and restarted servers. Then it corrected itself: demand had not surged. Servers had unexpectedly dropped out.

Second theory: health check failure

Servers were failing automated tests and removing themselves from service.Microsoft pointed to the component that processes server health.It found no recent change linked to the trouble.

The blast radius spreads

Copilot could not reach work data.Defender's Safe Links could not verify URLs.Purview's data-loss prevention, labelling and eDiscovery tools were hit.Intune enrolment, Graph API calls, Planner, To Do and Universal Print all failed.

Calendars down, but Teams calls held

Teams calls largely held up, but calendars did not.This meant everyone could complain about the outage, but IT could not resolve it.Files in SharePoint stayed accessible.

Microsoft: no malicious activity detected

Microsoft said it was not aware of any malicious activity causing the incident. The company said it would treat the incident with urgency and priority until full resolution, then provide full details of the root…

“We are not aware of any malicious activity that is causing this incident.”