On Thursday 12 November 2026, a widespread Microsoft 365 outage left businesses around the world struggling to send and receive email and reach collaboration tools. This article summarises what has been confirmed by Microsoft and by news reports, and clearly marks what is still unconfirmed.
What was affected
Microsoft opened Exchange Online incident EX1550543 and the Microsoft 365 suite advisory MO1550821. Services reported as potentially impacted include:
- Exchange Online (the email service behind business Outlook accounts)
- Microsoft Teams
- SharePoint Online
- Microsoft Copilot 365
- Microsoft Defender XDR
- Microsoft Planner and Microsoft To Do
Some outlets also list Microsoft Purview, Intune, Defender for Office 365 and the Microsoft 365 admin centre, but these were not consistently reported across sources.
When it started and where
The disruption began in the early afternoon, US Eastern Time, on 12 November (early 13 November in Australia). Reports differ on the exact minute, ranging from roughly 11:17 a.m. to about 1 p.m. ET for the first user reports, so we do not give a single definitive start time. The official Microsoft 365 Status account first said it was investigating problems accessing Exchange Online mailboxes "through multiple connection methods in the Americas". Microsoft later said the issue could affect Microsoft 365 services in any region, and reports describe a global impact.
Scale of the impact
Outage tracker Downdetector recorded a peak of about 128,874 Outlook problem reports according to Techaeris, and close to 130,000 according to other outlets (one report cites over 131,000). Downdetector counts user-submitted reports, not the number of affected customers. Microsoft has not published the total number of affected users, so that figure is unconfirmed.
What Microsoft has said about the cause
Microsoft's incident notes described the problem in stages:
- At first, it said a portion of infrastructure was experiencing elevated load across multiple regions.
- It then said a large number of servers were unexpectedly unavailable, shifting load onto the remaining infrastructure, and that the failed health checks might originate from a specific component responsible for processing server health. One update said a recent change to that component might be related.
- Microsoft said it had not identified a recent change correlated with the start of the impact, and reported that the problem was not a surge in demand.
- Later updates said engineers were assessing whether reverting a small number of recent configuration updates could speed recovery.
The root cause has not been confirmed. No cyberattack has been confirmed or claimed, according to reporting at the time, and Microsoft has not attributed the outage to one.
Recovery efforts and current status
Microsoft paused deployments, moved traffic off affected infrastructure, redistributed connection traffic and began restarting servers. It reported that it validated an alternative health-check method that allowed a subset of affected servers to return to service, was applying it more broadly, and was preparing an automated process to identify and restart servers that stop responding. At one point in the evening, Microsoft said actions taken so far had "not provided the anticipated relief". A later report said servers were being returned to service and some portions were stable as of 11:38 p.m. GMT on 12 November.
At the time of writing, we could not find a verified Microsoft statement declaring the incident fully resolved, so full restoration is unconfirmed. Several search results describe restorations, but they relate to earlier, separate Microsoft outages and are not used here.
What administrators and users can do
- Check the Microsoft 365 admin centre service health page for EX1550543 and MO1550821, which hold the authoritative, tenant-specific updates.
- Follow the Microsoft 365 Status account on X for public updates.
- Have a fallback channel for urgent communication, for example phone or a second messaging tool, while mail and Teams are unreliable.
- Expect some delayed email delivery after recovery, and check that important messages arrived.
This article reflects information available at the time of writing and will be out of date as Microsoft publishes new updates.
Sources
- Microsoft 365 Status on X: initial Exchange Online notice (EX1550543)
- Microsoft 365 Status on X: server restart and configuration update review (EX1550543, MO1550821)
- ABC7: Microsoft outage live updates
- Techaeris: Microsoft 365 Outage Takes Down Outlook, Teams and Copilot
- Engadget: Multiple Microsoft 365 services are experiencing an outage
- HCAmag: Microsoft outage disrupts Outlook and Teams for businesses worldwide
- Mitchell Now: Microsoft 365 outage, 12 November 2026
- Interesting Engineering: Microsoft outage affects 130,000 users as server failures spread
