Microsoft Outlook Outage Leaves Thousands Without Email as Servers Fail Health Checks
Microsoft Outlook went down for thousands of users on Thursday, 12 November 2026, after a large number of the company’s servers failed automated health checks. The failure disrupted Outlook email, Microsoft Teams, SharePoint, OneDrive and the Microsoft 365 Copilot assistant, leaving businesses, schools and government offices without core workplace tools for hours.
Microsoft acknowledged the problem during the afternoon in the United States and said engineers were restarting affected servers and redirecting traffic. Recovery was gradual, and by the morning of Friday, 13 November, the company had not confirmed that all services were fully restored.
Microsoft Outlook Outage — Quick Reference Summary
| Detail | What is known |
|---|---|
| Event | Microsoft 365 and Outlook outage |
| Date started | Thursday, 12 November 2026; user reports spiked from around 12:39 p.m. ET |
| Services affected | Outlook, Exchange Online, Microsoft Teams, SharePoint Online, OneDrive, Microsoft 365 Copilot |
| Peak user reports | Nearly 140,000 Outlook reports on Downdetector at around 1 p.m. ET; Microsoft 365 reports topped 47,000 |
| Cause given by Microsoft | A large number of servers failed automated health checks, leaving remaining infrastructure under elevated load |
| Incident references | EX1550543 (Exchange Online) and MO1550821 (wider Microsoft 365 advisory) |
| Cyberattack suspected? | No — Microsoft said there was no indication of a cyberattack |
| Status on 13 November | Gradual recovery under way; full restoration not yet confirmed |
How the outage unfolded on Thursday afternoon
Complaints about Outlook began spiking at around 12:39 p.m. Eastern Time on 12 November, according to reports of Downdetector data. At 12:54 p.m. ET, the Microsoft 365 Status account on X acknowledged that users were struggling to reach Exchange Online mailboxes in the Americas.
The scale of the disruption grew quickly. Downdetector recorded nearly 140,000 Outlook problem reports at around 1 p.m. ET, while reports about Microsoft 365 as a whole topped 47,000. Microsoft opened a wider advisory, tracked as MO1550821, at 1:26 p.m. ET, naming Exchange Online, Teams, SharePoint Online, Microsoft 365 Copilot and Defender XDR among the affected services.
Reports fell through the evening but did not disappear. More than 28,000 users were still reporting Outlook problems at around 9 p.m. ET, according to USA Today’s live coverage of the outage. Microsoft said it was seeing positive results from restarting affected infrastructure, while warning that users could keep experiencing disruption as servers returned to service.
The servers behind the failure: what Microsoft has said so far
Microsoft traced the outage to its own infrastructure rather than to a surge in user demand. The company said a portion of its infrastructure was experiencing elevated load across multiple regions, and later explained that the load was caused by servers becoming unexpectedly unavailable and straining the systems that remained online.
Engineers subsequently narrowed the fault to a component responsible for processing server health. Microsoft carried out a full reset of the affected servers and paused deployments while it worked on the problem. In its later updates, however, the company said the first change had not taken effect as expected, and that it was identifying alternate workstreams and preparing another configuration adjustment to increase capacity.
A company spokesperson told the Australian Broadcasting Corporation there was no indication the outage was a cyberattack. Australian Home Affairs Minister Tony Burke later said Microsoft did not believe the disruption was caused by a cyber event, and no evidence of an attack has been reported.
Hospitals, state offices and schools felt the disruption first
The outage landed in the middle of the working day in the Americas, and organisations that depend on Outlook felt it immediately. In the United States, the Michigan Department of Technology, Management & Budget said state government was having trouble with email and other Microsoft applications, while Michigan Medicine reported problems reaching Outlook and other Microsoft applications.
Sources told The Detroit News that Henry Ford Health lost access to Outlook and Teams. The disruption also reached Australia by Friday morning, where Service NSW reported that some transactions at its service and call centres were unavailable. Some users said the Outlook failure also locked them out of other services because they could not receive two-factor authentication codes by email.
The knock-on effect on OpenAI, Anthropic and company results
The outage spread beyond Microsoft’s own products because other services depend on its connectors. OpenAI said it was investigating an issue with Microsoft connectors in which new connections could break and tools might not work as expected, while Anthropic said it had identified an issue with an upstream provider affecting its Microsoft 365 connector.
Businesses also felt the disruption in their reporting calendars. Electric truck maker Workhorse Group, which had been expected to report third-quarter results on 12 November, rescheduled the announcement to 16 November, citing business disruptions caused by the outage. Microsoft shares fell 0.2 percent in overnight trading late on Thursday.
What users can do while services recover
Microsoft has told users to expect a gradual restoration as servers return to service, with some people regaining access before others. Anyone still locked out of Outlook can check the Microsoft 365 Status account on X or the Microsoft 365 admin centre under incident references EX1550543 and MO1550821 for the latest update.
Users who rely on Outlook for two-factor authentication codes should keep an alternative sign-in method ready, such as an authenticator app, until email access is stable again. Organisations running on Microsoft 365 should also confirm that Teams meetings, shared files and calendars are syncing normally before treating the incident as over.
Frequently asked questions
Is Microsoft Outlook still down?
Recovery was under way on the morning of Friday, 13 November, but Microsoft had not confirmed full restoration. Some servers had returned to service and reports were falling, yet thousands of users were still reporting problems late on Thursday evening.
Was the Microsoft outage caused by a cyberattack?
No evidence of a cyberattack has been reported. Microsoft said a large number of servers failed automated health checks, and a spokesperson told the ABC there was no indication of an attack.
Which Microsoft services were affected?
Outlook and Exchange Online were hit hardest, along with Microsoft Teams, SharePoint Online, OneDrive and Microsoft 365 Copilot. Microsoft also listed Defender XDR in its wider advisory, and connectors used by OpenAI and Anthropic were disrupted.
How many users were affected?
Downdetector, which counts user-submitted reports rather than affected accounts, logged nearly 140,000 Outlook reports at the peak at around 1 p.m. ET on 12 November, with Microsoft 365 reports topping 47,000. Reports were logged from 74 countries and territories.
When will Outlook be fully back?
Microsoft has not given a firm time. The company said it was restarting affected servers and preparing further configuration changes, and warned that restoration would be gradual as clients reconnected.
