A Microsoft 365 outage that began around midday Eastern time on Thursday, November 12, 2026, cut many users off from Outlook and Exchange Online mail and spilled into Teams, Copilot, SharePoint and more than a dozen other Microsoft services. Microsoft tracks it as incident EX1550543 for Exchange Online and MO1550821 for Microsoft 365, according to the Microsoft 365 Status account on X.
Status as of 10:11 p.m. ET, November 12: not resolved. The Microsoft 365 service health status page lists "Service degradation" for Microsoft 365 business and enterprise services and for consumer products. Its latest business update, posted at about 10:07 p.m. ET, says a change meant to improve service "is not taking as expected" and that Microsoft is looking for other ways to add capacity. Microsoft has not given a time for full recovery.
The short version: check Service health in your admin center, or the public status page if the admin center will not load. Tell staff it is a Microsoft problem, not theirs. Move urgent work to a backup channel. Do not reset passwords or reinstall Outlook to fix it. Watch for phishing that uses the outage as bait, and plan to read Microsoft’s post-incident report.
What happened in the Microsoft 365 outage
Microsoft first posted at 12:54 p.m. ET. It was investigating "issues accessing Exchange Online mailboxes through multiple connection methods in the Americas." At 1:07 p.m. ET it said the issue "may affect Microsoft 365 service connectivity for users in any region."
The cause Microsoft has described so far is servers dropping out of service. In a post at 2:31 p.m. ET, Microsoft said the elevated load "isn’t driven by an increase in traffic, but by a number of servers being unexpectedly unavailable." The remaining servers took the strain.
Later posts narrowed it down. Microsoft said the servers were failing automated health checks, and that the failures "may originate from a specific component that’s responsible for processing server health." At 5:09 p.m. ET, Microsoft wrote that "a core process on affected servers is becoming overwhelmed, causing capacity loss." Microsoft has not published a root cause.
Timeline of the Microsoft 365 outage in ET
All times below are Eastern, on November 12, from Microsoft 365 Status posts on X unless noted.
- 10:40 a.m. A separate Teams incident, TM1550488, for users in North America. ABC News reports Microsoft later said that service was restored.
- 12:54 p.m. Exchange Online mailbox access issues in the Americas (EX1550543).
- 1:07 p.m. Impact may reach users in any region.
- About 1:27 p.m. Downdetector shows more than 130,000 Outlook reports, according to TechRepublic, citing Reuters.
- 1:35 p.m. Elevated load across multiple regions. Microsoft adds incident MO1550821.
From mid-afternoon, Microsoft’s posts track the recovery work.
-
2:12 p.m. Microsoft pauses all deployments, moves traffic off affected infrastructure and restarts servers.
-
2:50 p.m. Testing a configuration change while restarting all affected servers.
-
3:19 p.m. No recent change correlated with the start of impact.
-
4:00 p.m. An alternative health check method returns some servers to service.
-
4:40 p.m. Assessing whether reverting "a small number of recent configuration updates" could speed recovery.
By early evening, Microsoft said the first fixes were not enough. -
5:09 p.m. Actions so far "have not provided the anticipated relief."
-
6:04 p.m. Some servers returned to service and stable "so far."
-
7:06 p.m. Returned servers "can become unresponsive again once they receive traffic." Microsoft limits some traffic types and rebuilds a subset of servers on a previous configuration.
-
8:59 p.m. Microsoft reports "positive results" from restarting infrastructure in an isolated way.
-
9:14 p.m. Status page update: capacity improvements to support "traffic in regions coming online."
-
10:07 p.m. Latest status page update: the change "is not taking as expected," and Microsoft is "identifying alternate workstreams" to add capacity. Next update by 10:30 p.m. ET.
Which Microsoft 365 apps and services are affected
Microsoft’s status page says features that use Exchange Online and email are affected. Parts of each service that do not depend on Exchange Online "remain functional." Here is what Microsoft lists for business and enterprise tenants.
| App or service | What users may see, per Microsoft | Source |
|---|---|---|
| Exchange Online and Outlook | No mailbox access in Outlook on the web, Outlook desktop (MAPI), Exchange ActiveSync or REST; delayed mail delivery | status.cloud.microsoft |
| Microsoft Teams | Calendar, meeting scheduling and some Exchange-dependent features may fail; core chat and online meetings “remain largely functional” | status.cloud.microsoft |
| Microsoft 365 Copilot | Copilot Chat may not load or respond; Copilot may not reach email, calendar and files | status.cloud.microsoft |
| SharePoint Online | Exchange-dependent features may fail; files stored in SharePoint still open | status.cloud.microsoft |
| Microsoft 365 admin center | Some admin pages may not load | status.cloud.microsoft |
| Defender for Office 365 | Safe Links may not verify URLs clicked in Outlook and Teams | status.cloud.microsoft |
| Planner, To Do | Plan and task failures; To Do may not load | status.cloud.microsoft |
| Microsoft Graph | API calls that read mail, calendar or contacts may time out | status.cloud.microsoft |
The same page also names Microsoft 365 apps (recently used files), the Microsoft 365 Apps Admin Center, Microsoft 365 Education, Defender XDR, Microsoft Fabric, Intune, Purview, Power BI, Universal Print and Windows 365 with Purview Customer Key. For consumer accounts, Microsoft lists Outlook.com, OneDrive, OneNote, To Do, Teams and Microsoft 365 for the web.
How to confirm the Microsoft 365 outage hits your tenant
Start with Service health. In the Microsoft Learn guide to service health, the path is the Microsoft 365 admin center, then Health and Service health. Search for EX1550543 and MO1550821. If they appear for your tenant, Microsoft has tied your tenant to the incident.
If the admin center will not load, use the public status page. Microsoft says it posts there because "administrators may be unable to access the admin center." The Microsoft 365 Admin app on a phone also shows Service health, per the same Learn page.
Read the status labels. Microsoft Learn defines "Service degradation" as a confirmed issue that "might affect use of a service or feature." "Service interruption" means users cannot reach the service. "Service restored" means Microsoft confirmed a fix. "Post-incident report published" means a root cause report is out.
Downdetector is useful as a signal, not proof. Its counts are user reports, not a count of affected people. A drop in reports does not mean your users are back. Trust Service health for your tenant.
What nonprofit and association IT teams should do now
Small IT teams carry most of the load during a Microsoft 365 outage. Start with these four steps.
- Tell staff once, early. Send a short note by text, Slack, phone tree or a personal channel your org already approved. Say it is a Microsoft problem and give a time for the next update.
- Use the backup channel you planned. Move urgent member, donor and event messages to phone or a second tool. If Teams chat works, use it, since Microsoft says core messaging is largely working.
- Let Outlook run in cached mode. Microsoft Support says Cached Exchange Mode keeps a local copy of the mailbox. Staff can read older mail when the connection is "slow or unavailable." It is not available in new Outlook for Windows.
- Do not reset passwords or reinstall Office. Microsoft has placed the cause in its own servers. Resets, new profiles and reinstalls add work and fix nothing.
Three more checks matter while the Microsoft 365 outage runs.
- Do not switch to Outlook on the web as a fix. Microsoft lists Outlook on the web among the affected connection methods.
- Watch for outage-themed phishing. Expect fake "reconnect your mailbox" messages that use the Microsoft 365 outage as bait. Tell staff not to enter passwords from links in those emails. Microsoft says Safe Links checks may also be affected.
- Log the impact. Note which teams were down, for how long, and what missed deadlines or event emails it caused.
What to do after the Microsoft 365 outage
Wait for Service health to show "Service restored." Then check a few mailboxes, shared mailboxes and room calendars. Confirm delayed mail arrived. Check automation that uses Microsoft Graph or Exchange. Think AMS sync jobs, forms that send mail, and event reminders. They may have failed quietly.
Then ask for the post-incident report. Microsoft Learn says this status means Microsoft has published root cause information and next steps. Read it, and file it with your own impact log. If you use an MSP, ask it to send you both.
Last, review your plan for the next one. Our post on data backup strategy basics covers keeping copies outside one platform. Mail changes are also coming on their own timeline: the Exchange Online EWS retirement is underway, and on-premises admins had the Exchange Server October update issue. If an MSP manages your tenant, the questions in our MSP Process breach post apply here too: who has admin access, and how they reach you when Microsoft 365 is down.
What press reports add
Press coverage fills in the scale of the Microsoft 365 outage. These numbers are not Microsoft’s. TechRepublic, citing Reuters, reports more than 130,000 Outlook reports on Downdetector around 1:27 p.m. ET, plus more than 46,000 for Microsoft 365 and about 3,000 for Teams. Al Jazeera, also citing Reuters, says reports fell to about 77,000 just before 3 p.m. ET. NBC Chicago reported more than 22,000 reports early on, with hot spots in Chicago, Seattle and New York. ABC News reports that NYC Emergency Management warned of delays in email and online city services.
Frequently Asked Questions
Is the Microsoft 365 outage over?
Not as of 10:11 p.m. ET on November 12. Microsoft’s status page still showed “Service degradation.” Check Service health or status.cloud.microsoft for the latest.
What are the incident IDs?
EX1550543 for Exchange Online and MO1550821 for Microsoft 365. An earlier Teams incident that morning was TM1550488.
What caused it?
Microsoft says servers became unavailable after failing health checks, and a core process on them was overwhelmed. It has not published a root cause yet.
Was it a cyberattack?
Microsoft has not said so. Its posts describe server and health check problems. Wait for the post-incident report.
Should staff reset their passwords?
No. The problem is on Microsoft’s side. A reset will not restore mail.
Can staff read old email?
Often, yes. Outlook in cached mode keeps a local copy, so older mail stays readable. New mail waits until service returns.
Did the Microsoft 365 outage affect Teams?
Partly. Microsoft says Teams features tied to Exchange, like calendars and scheduling, may fail, while core chat and meetings remain largely working.
Will we lose email sent during the Microsoft 365 outage?
Microsoft says delivery “may be delayed.” It has not reported lost mail. Check that delayed mail arrives once service is restored.
