Microsoft Outlook went dark for tens of thousands of people across the United States on Thursday, November 12, 2026, in a widespread outage that also knocked out Microsoft 365, Teams and Copilot for hours. Reports of failed inboxes surged just after noon Eastern time and peaked at roughly 130,000, as users found they could not open their mail or send messages.

The failure struck mid-workday, when email is the backbone of offices, schools and government agencies. By evening, Microsoft said it was returning some servers to service and reports were falling, but it gave no firm time for full restoration and no root cause.

Key Points

• Downdetector reports for Outlook peaked at about 128,874 to 130,000 around 1:09 to 1:27 p.m. ET on Thursday, November 12, 2026.
• Microsoft 365 reports topped 46,000 and Teams reports reached about 3,000 at the height of the disruption.
• Microsoft traced the failure to Exchange Online mailboxes in the Americas, tracked as incident EX1550543.
• By about 6 p.m. ET, reports had fallen to roughly 32,500 for Outlook and 11,300 for Microsoft 365 as Microsoft returned some servers to service.
• The outage also broke connectors used by OpenAI and Anthropic AI services, and no root cause had been disclosed.

What Happened

Reports began surging just after noon ET on Thursday, as people across the United States tried to open their inboxes and found nothing loading. Users could not send or receive email, and many could not reach the work apps tied to their Microsoft accounts. Within about an hour, reports on Downdetector peaked at between 128,874 and 130,000 for Outlook around 1:09 to 1:27 p.m. ET.

Microsoft confirmed it was investigating problems with Exchange Online mailboxes in the Americas, the cloud service that powers Outlook email. The company said a number of servers unexpectedly became unavailable and failed automatic health checks, leaving the remaining infrastructure strained under the load. Part of the system that stores and delivers mail simply dropped out, and the servers left standing could not carry the full weight.

Microsoft 365 drew more than 46,000 reports, Teams about 3,000, and the outage broke connectors used by OpenAI and Anthropic AI services. By about 6 p.m. ET, Microsoft said it was returning a portion of the affected servers to service, and Outlook reports had fallen to about 32,500.

Background and Context

Exchange Online is the cloud email engine behind Outlook and much of Microsoft 365. When a business, school or government office uses Outlook, its messages live on Microsoft's servers, not on a computer in the building. That makes email available anywhere, but it also means a failure inside Microsoft's data centres can silence inboxes across a whole continent at once.

Microsoft 365 has become the default workplace for a huge share of American offices. Email, calendars, video meetings, shared documents and the Copilot AI assistant all run through the same account and the same cloud. When the mail servers falter, meetings are missed, invoices sit unsent, and teams lose the thread of inbox conversations.

Microsoft Outlook Outage: The Scale of the Failure

A peak of roughly 130,000 Outlook reports is far beyond the background noise of everyday glitches, and the 46,000 reports for Microsoft 365 show the problem was not limited to one app. Even at 6 p.m. ET, hours after the first reports, about 32,500 people were still reporting Outlook problems, a sign that recovery was partial rather than complete.

Microsoft described the incident as centred on the Americas, which matches where the reports were concentrated. The company has not said how many mailboxes were affected in total, and Downdetector counts reports rather than users, so the true number of people locked out of their email is likely higher than the figures shown.

Reactions and Quotes

Microsoft's own status update was blunt about the cause, saying a number of servers "unexpectedly became unavailable and failed automatic health checks" and that the failure was straining the remaining infrastructure. The company framed the response as a staged recovery, bringing servers back into service in portions rather than all at once.

Frustrated users turned to Downdetector and social media to check whether the problem was theirs or Microsoft's, and quickly found they were far from alone.

Why It Matters

Email remains the spine of American working life, even in an age of chat apps and video calls. Contracts, invoices, job offers, medical appointments and school notices still travel by email, and a half-day without it can stall decisions that cannot wait. An outage at midday on a Thursday hits offices at full speed, not in the quiet hours when few would notice.

The failure also matters because so much now depends on a small number of cloud providers. When Microsoft's mail servers go down, there is no easy backup for most users: the inbox is the service, and switching providers mid-workday is not realistic. For Microsoft, the timing is awkward too.

What Happens Next

Microsoft is expected to keep bringing affected servers back into service in stages, with problem reports falling as mailboxes come back online. The company will likely publish a fuller explanation once the incident is closed, including what knocked the servers offline and what it will change to stop it happening again. Users should watch Microsoft's service health page for the official all-clear.

For people still locked out, the advice is simple: do not delete accounts or reinstall apps in a panic, since the fault sits on Microsoft's side.

Frequently Asked Questions

How many users were affected by the Microsoft Outlook outage?
Downdetector reports for Outlook peaked at about 128,874 to 130,000 around 1:09 to 1:27 p.m. ET on Thursday, November 12, 2026, with Microsoft 365 reports topping 46,000.

What caused the outage?
Microsoft said a number of servers unexpectedly became unavailable and failed automatic health checks, straining the remaining infrastructure for Exchange Online mailboxes in the Americas.

Teams drew about 3,000 problem reports during the outage, and Copilot was affected too.

Is Outlook back now?
Service was partly restored by about 6 p.m. ET, with reports falling to roughly 32,500 for Outlook, but Microsoft gave no firm time for full restoration.

Microsoft said the outage broke connectors used by OpenAI and Anthropic AI services, so tools that plug into Microsoft's systems were disrupted alongside email.

Related coverage: Microsoft has been expanding the cloud and AI systems behind its workplace tools, and recently pressed the White House over a planned ban on Chinese optical transceivers that it warned could stall its AI data centre buildout. The AI industry is also watching how closely its tools are tied to Microsoft's cloud, as Nvidia's independent probe into claims around its chief executive continues, and as Google, OpenAI, Microsoft and Anthropic back a single no-scrape signal for AI training data.