Is Microsoft 365 Down? What We Know About the November 12 Outage
TL;DR
The outage was not caused by a traffic surge. Microsoft said the "elevated load" came from servers being "unexpectedly unavailable," straining the remaining infrastructure. Downdetector reports for Outlook peaked at about 129,000 just after 1 p.m. ET. Microsoft paused all deployments, moved traffic away from affected infrastructure, restarted servers, and tested a configuration change, and later said it had validated an alternative health-check method on some servers. Microsoft 365 has roughly 321 million users, according to Dynamics Connect.
- Incident IDs: EX1550543 (Exchange Online) and MO1550821 (broader Microsoft 365), plus a separate morning Teams incident, TM1550488.
- A post-incident report is expected to provide the final root cause.
On Thursday, November 12, 2026, Microsoft 365 suffered a widespread outage that hit
Outlook (Exchange Online),
Teams,
SharePoint Online,
Microsoft 365 Copilot and Defender XDR,
starting with Americas mailbox problems and spreading to users in any region.
Microsoft says
A large number of its servers became unexpectedly unavailable after failing automated health checks, which strained the rest of its infrastructure.
It has not named a root cause, and nothing it has published points to a cyberattack. Restoration was still underway in the latest reports reviewed, so check the Microsoft 365 Service Health page for current status.
What Is the Timeline?
Here are the reported times (Eastern):
Time | Event |
|---|---|
Morning | A separate Teams incident (TM1550488) affects users in the Americas; Microsoft later marks it resolved and does not say whether the two are linked |
11:17 a.m. | Microsoft opens EX1550543: users may be unable to connect to Exchange Online mailboxes through multiple methods |
12:39 p.m. | Outlook problem reports begin climbing on Downdetector |
About 1:07 p.m. | Microsoft says users in any region could be affected |
About 1:09 p.m. | Outlook reports peak at about 128,874 |
By about 2 p.m. | Microsoft says the elevated load comes from servers failing automated health checks, pauses deployments and begins restarting servers (Fox Business) |
About 3:19 p.m. | Microsoft says no recent change lines up with the start, and the failed checks may come from a component that processes server health |
3:56 p.m. | Not fully restored; Microsoft applying an alternative health-check method more broadly |
4:41 p.m. | Affected list grows to include Intune, Defender for Office 365, Purview and Power BI; incident still open, no root cause published |
What Did Microsoft Say Caused It?
Servers failing health checks, with the reason still unexplained. According to Microsoft's updates, a number of servers failed automated health checks and became unavailable, which pushed load onto the rest of the infrastructure.
Microsoft said
It had "not identified any recent change correlated with the start of impact," and that the failed checks may come from a specific component that processes server health.
It paused all deployments and began redistributing connection traffic. One outlet reports a later Microsoft update pointing to a process that sets up secure connections on each server, but that appears in a single source, so treat it as unconfirmed.
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Book a Free ConsultationWhich Services Were Affected?
Mail, chat, files, AI, and security tools. Microsoft's service health notices listed:
Exchange Online and Outlook (web, desktop, mobile and API connections)
Microsoft Teams, SharePoint Online, Planner and To Do
Microsoft 365 Copilot
Defender XDR, Defender for Office 365 and Purview
Later: Intune and Power BI
User reports also named OneDrive and Azure, but Microsoft's own affected list in the coverage reviewed did not include Azure. Downdetector also showed problems with Xbox and Amazon, and it was unclear whether they were related.
Was It a Cyberattack?
There is no evidence of one. Microsoft's published updates focus on unavailable servers and failed health checks, and nothing it has said points to an attack. Until Microsoft publishes a post-incident review, the accurate position is that there is no evidence of an attack and no full root cause either.
Is It Fixed Yet?
Not confirmed as of the latest reports reviewed. By around 3:30 p.m. ET, Microsoft was restarting servers and restoring service, and Tom's Guide described the outage as winding down. But a 4:41 p.m. ET update still showed the incident open with no root cause. Check the Microsoft 365 admin center and Microsoft 365 Status on X for live updates, since this article may be out of date.
Has Microsoft 365 Had Other Outages This Year?
Yes, according to compiled coverage. Past 2026 incidents include a January 22 capacity issue affecting Outlook and Teams, a June 2 mail-flow problem where some messages stayed undelivered for over an hour, and an August 31 authentication configuration issue in Exchange Online. This is as reported by TechRadar and by a summary of BleepingComputer's coverage, and it shows how often large cloud services suffer wide incidents.
What Should IT Teams Do Right Now?
Focus on communication and continuity, not changes.
Check Service health in the admin center for EX1550543 and MO1550821, and watch for the post-incident report
Use backup communication such as phone, SMS, or a non-Microsoft chat tool for urgent messages
Avoid configuration changes during the incident unless Microsoft advises them
Document the impact with times and affected services, for SLA and internal review
Tell staff what is and is not working, and where to get updates
For mail, sending servers often retry delivery, so delays are more likely than loss, but confirm in Microsoft's post-incident report rather than assuming.
What Does This Mean for Copilot and AI Workflows?
AI assistants depend on the same cloud. Microsoft 365 Copilot was on the affected list, which means AI features built on Microsoft 365 can fail with it. If your team relies on Copilot or Copilot-based agents, plan a manual fallback for critical tasks. Single-vendor dependence is a risk across AI tools, as our coverage of ChatGPT, Claude, and Grok going down together showed.
Our AI services and solutions, and agentic AI development teams can help you design AI workflows with fallbacks and clear escalation paths.
Frequently Asked Questions
Is Microsoft 365 down right now?
It was affected on November 12, 2026, and restoration was in progress in the latest reports reviewed. Microsoft was restarting servers and applying a different health-check method, but a 4:41 p.m. ET report still showed the incident open. Check the Microsoft 365 Service health page in your admin center or the Microsoft 365 Status account on X for live status.
What caused the Microsoft 365 outage?
Microsoft says a large number of servers became unexpectedly unavailable after failing automated health checks, which strained the remaining infrastructure. It said the load was not caused by increased traffic and that it had not identified a recent change correlated with the start. Microsoft has not named a root cause, and a post-incident report is expected.
Was the Microsoft outage a cyberattack?
There is no evidence of a cyberattack. Nothing Microsoft has published points to one, and its investigation focuses on unavailable servers and failed health checks. The honest answer until Microsoft releases its post-incident review is that the cause of the servers' failure is not yet explained.
Which Microsoft services were down?
Exchange Online (Outlook), Teams, SharePoint Online, Microsoft 365 Copilot, and Defender XDR, plus Planner, To Do, and Purview, according to Microsoft's service notices. Later Microsoft added Intune, Defender for Office 365, and Power BI. Users also reported OneDrive and Azure problems, though Microsoft's list in the coverage reviewed did not include Azure.
How many people were affected?
Downdetector showed about 129,000 Outlook reports at the peak, just after 1 p.m. ET, though these are user reports, not a count of affected accounts. Microsoft 365 has roughly 321 million users globally, according to Dynamics Connect. Microsoft has not published a number of affected customers.
What are the Microsoft incident numbers for the outage?
EX1550543 covers Exchange Online mailbox connectivity, and MO1550821 covers broader Microsoft 365 connectivity. A separate Teams incident, TM1550488, affected users in the Americas earlier in the day and was marked resolved. Admins can find these in the Microsoft 365 admin center under Service health.
Will I lose emails because of the outage?
Delays are more likely than loss, but confirm with Microsoft. Sending mail servers commonly retry delivery for some time, but Microsoft has not said whether any messages were lost. Watch for its post-incident report, and check with important senders if you are expecting time-sensitive messages.
What should my business do about Microsoft 365 outages?
Prepare a continuity plan: backup communication channels, a contact list outside Microsoft 365, a process for checking Service health, and a record of impact for SLA reviews. For AI tools such as Copilot, define manual fallbacks for critical tasks, and avoid making configuration changes during an active incident.
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