TL;DR: Microsoft 365 went down for thousands of users starting around 12:30 p.m. ET on Thursday, November 12, knocking out Outlook, Teams, SharePoint Online, Copilot 365 and Defender XDR for both personal and business accounts. Downdetector logged more than 131,000 reports for Outlook alone. Microsoft spent the afternoon testing configuration changes and pausing all deployments across Microsoft 365, and more than three hours in, it still hadn’t pinned down a root cause.
If your inbox stopped loading around lunchtime today, you weren’t imagining it. Microsoft 365 suffered a multi-hour outage that started close to 12:30 p.m. ET on November 12, pulling down Outlook, Teams, SharePoint Online, Copilot 365 and even Defender XDR, Microsoft’s enterprise security platform, for a chunk of the workday.
Downdetector’s tracker for Outlook climbed past 131,000 user reports at its peak, while complaints about Microsoft 365 broadly topped 47,000 around 1:20 p.m. ET. Teams added roughly 2,000 more reports and Copilot another 4,400. Those figures blend personal Outlook.com accounts with corporate Exchange Online mailboxes, which is part of why this one felt bigger than Microsoft’s usual regional hiccups. It hit home users and enterprise IT departments at the same time, on a Thursday afternoon.
Microsoft first acknowledged the problem at 12:54 p.m. ET, saying on its Microsoft 365 Status account that it was “investigating reports of users experiencing issues accessing Exchange Online mailboxes through multiple connection methods in the Americas,” filed under incident ID EX1550543. Thirteen minutes later, the company widened the scope in its own language, warning the issue “may affect Microsoft 365 service connectivity for users in any region.”
By 1:35 p.m. ET, Microsoft said a portion of its infrastructure was “experiencing elevated load across multiple regions,” and it began redistributing traffic worldwide about 13 minutes after that. That’s usually the point where an outage either clears quickly or turns into an afternoon-long slog. This one took the second path.
Just before 3 p.m. ET, Microsoft said it was testing a configuration change and restarting affected servers at the same time, a sign engineers still weren’t certain which fix would actually work. By 3:14 p.m. ET, the company had paused all deployments and configuration changes across Microsoft 365, company-wide, while it kept working the problem, and promised another update by 5 p.m. ET.
The most telling line came at 3:35 p.m. ET, when Microsoft’s status account said it had “not identified any recent change correlated with the start of impact.” In plainer terms, more than three hours into an outage that locked millions of people out of their email, the company running the service still didn’t know what broke. Microsoft’s working theory points at failed health checks that “may originate from a specific component” responsible for monitoring server health, which would mean part of the system meant to catch problems early may have triggered this one instead.
If you’re trying to work out whether this is really Microsoft’s problem and not something local to your own network, the fastest way to check is the Microsoft 365 admin center’s Service Health dashboard rather than Downdetector. Microsoft updates that page directly as its engineers learn more, and IT admins saw the same incident ID, EX1550543, logged there. That’s the reference number worth citing if you’re opening a support ticket or explaining the outage to people at your own company.
Teams relying entirely on Microsoft’s stack felt this one the hardest. Remote and hybrid workforces that run their calendars through Outlook, their meetings through Teams and their files through SharePoint don’t have an obvious fallback channel when all three go sideways at once. Slack and Google Workspace users mostly carried on with their afternoon unaffected, which is its own quiet argument for not putting every piece of a company’s communication stack on a single vendor.
Defender XDR going down alongside Outlook matters beyond simple inconvenience. It’s Microsoft’s extended detection and response platform, the tool many of the same companies locked out of their email rely on to watch for intrusions in real time. A multi-hour gap in security monitoring, even one caused by an internal glitch rather than an attack, is the kind of blind spot security teams usually plan around rather than live through.
Copilot’s involvement is worth flagging too. A year ago, an Exchange hiccup like this one would have meant people couldn’t read email for a few hours and little else. Now Copilot is wired into Outlook, Teams, SharePoint and Word, summarizing threads, drafting replies and surfacing meeting notes. When the services underneath wobble, the AI layer sitting on top wobbles with them, and Microsoft hasn’t said whether its fix addressed Copilot directly or just rode along once Exchange Online stabilized.
It’s been a rough stretch for Microsoft’s reliability record either way. Just two days ago we covered the decade-old Paint vulnerability the company quietly patched, and now its flagship productivity suite is the one making headlines for the wrong reasons. This also isn’t the company’s first lengthy Microsoft 365 outage this year. A nearly 10-hour overnight outage in January 2026 took down similar services for North American users, though Microsoft attributed that incident to a different internal cause. Today’s episode had already run past three hours with no resolution confirmed, and a company promising its next update by 5 p.m. ET is usually a company that expects the problem to stretch into the evening.
The bigger pattern is one worth sitting with. When a handful of companies run the infrastructure most of the internet depends on, a single bad health check or an unexplained traffic spike can take down email, chat and security tooling for millions of people at once, with no cyberattack required. We saw a version of this when drone strikes knocked out Yandex’s data centers earlier this year, and Microsoft’s own incident fits the same lesson from a different angle: concentration is convenient right up until it isn’t.
For businesses, the timing stung. A midday, multi-hour outage across Outlook, Teams and Copilot during a weekday means missed meetings, stalled approval chains and, in some cases, AI workflows that quietly stopped responding without anyone noticing until something didn’t get done. Microsoft hasn’t said whether it will issue service credits or publish a formal post-incident report, which is standard practice after outages of this size and duration.
The bottom line
Outages happen to every cloud provider eventually, and Microsoft’s fast acknowledgment and relatively frequent status updates deserve some credit here. But admitting, more than three hours in, that engineers can’t tie the outage to any recent change is not a great look for a company whose entire pitch to enterprises is that they should trust it to run their email, their meetings and increasingly their AI assistants. If Outlook or Teams is still acting up for you this afternoon, you’re not alone, and there’s nothing on your end to fix. This one is squarely on Microsoft’s infrastructure team to sort out.
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