Outlook and other Microsoft 365 apps were still not fully back late on Thursday, Nov. 12, more than nine hours after Microsoft first acknowledged the email problem. At 10:13 p.m. ET, the company’s Microsoft 365 Status account said the changes it had applied were “not taking as expected” and that engineers were looking for other ways to add capacity. For anyone asking what happened to Outlook, Microsoft says a large number of its servers failed automated health checks and dropped out of service, which left the remaining servers overloaded. A Microsoft spokesperson told the Guardian and ABC News Australia there was no indication of a cyberattack.
A spike of nearly 140,000 reports
Microsoft’s status account first posted about the mailbox problem at 12:54 p.m. ET, citing users having trouble reaching Exchange Online mailboxes “through multiple connection methods in the Americas.” Thirteen minutes later it said the problem could affect Microsoft 365 users “in any region.”
Reports climbed quickly. The Associated Press said nearly 130,000 users had reported Outlook problems on Downdetector just after 1 p.m. ET. CNA put the peak at 138,058, and the BBC said nearly 140,000 around 18:00 GMT, which is the same hour. The figures likely reflect different snapshots of the same spike.
Many told AP they could not send or receive email or even load their inboxes. In Australia the trouble began just after 3 a.m. Friday local time, and the national cyber security coordinator, Lt. Gen. Michelle McGuinness, was looking into it, ABC News reported.
A separate, shorter Teams problem in North America came earlier in the day. Microsoft flagged it at 10:40 a.m. ET and called it resolved at 12:09 p.m. The Guardian also reported that Teams service there had been restored.
What Microsoft says broke
Microsoft’s explanation shifted during the day, as The Conversation noted. At first the company described “elevated load across multiple regions.” At 2:31 p.m. ET it said the load “isn’t driven by an increase in traffic, but by a number of servers being unexpectedly unavailable.” Its later posts said the failed health checks may come from a component that processes server health, and that “a core process on affected servers is becoming overwhelmed.”
A later Microsoft note, reported by India Today and ABC, said the process that sets up secure connections on those servers was getting swamped, so the servers stopped handling requests.
The picture on configuration changes is muddier. At 3:19 p.m. ET Microsoft posted that it had “not identified any recent change correlated with the start of impact.” By 4:40 p.m. it said it was weighing whether to revert “a small number of recent configuration updates.” India Today later reported that Microsoft had started reversing a recent network configuration change that coincided with the start of the outage. Microsoft has not said whether that change caused the outage. RMIT University engineering professor Mark Gregory told the Guardian he suspects a network misconfiguration, which is his view and not a Microsoft finding.
Which apps are hit and which still work
Engadget said Microsoft’s status page listed Exchange Online, Teams, SharePoint Online, Microsoft 365 Copilot and Defender XDR as possibly affected, and TechCrunch named the same core set. TechCrunch added that consumers were also cut off from OneDrive and Office for the web.
According to India Today’s summary of Microsoft’s notes, Outlook on the web, the Outlook desktop app and Exchange ActiveSync, which many phone mail apps use, can all fail, and email delivery may be delayed. Parts of Microsoft 365 that do not depend on Exchange Online keep working. The BBC said Microsoft described messaging and online meetings as largely functional.
Outside AI tools were hit too. OpenAI said new connections through its Microsoft connectors could be broken, and Anthropic said an upstream provider was affecting its Microsoft 365 connector, according to the Guardian and CNA.
The outage by the numbers
We pulled the main figures together from Microsoft’s own posts and news reports. Times are Eastern.
| Number | What it refers to | Source |
|---|---|---|
| 12:54 p.m. | Microsoft’s first post about the mailbox problem | Microsoft 365 Status on X |
| 1:07 p.m. | Microsoft says users in any region may be affected | Microsoft 365 Status on X |
| About 130,000 to 140,000 | Peak Outlook reports on Downdetector, around 1 p.m. | AP, CNA, BBC |
| 74 | Countries and territories with reported problems | CNA, citing Downdetector |
| About 37,000 | Outlook reports still logged at 6 p.m. | CNA |
| 10:13 p.m. | Microsoft says its fixes are “not taking as expected” | Microsoft 365 Status on X |
| EX1550543 and MO1550821 | Incident IDs for admins in the Microsoft 365 admin center | Microsoft 365 Status on X |
TechCrunch noted that a days-long Microsoft 365 outage in September was blamed on a “core authentication configuration” issue, and the Guardian mentioned an Azure outage last month.
What to do if your inbox is still down
The fault sits on Microsoft’s servers, so reinstalling Outlook or resetting your password is unlikely to bring mail back. These steps help more:
- Check Microsoft’s public status page or @MSFT365Status on X. Microsoft points people there when the admin center won’t load, and TechCrunch found it unreachable at one point.
- IT admins can follow incidents EX1550543 and MO1550821 for Microsoft’s impact list.
- Expect slow mail. Microsoft’s notes, as reported by India Today, warn of delivery delays, so phone or message people about anything urgent instead of resending.
- Try a Teams chat or meeting to reach coworkers, since the BBC said Microsoft described those as largely working.
- Ignore emails or texts offering an “outage fix” or asking you to sign in through a link.
Some Australian users told ABC they were locked out of other services because they could not receive two-factor codes.
Gregory told the Guardian that businesses should keep a backup, such as a second email account with another provider. Microsoft said at 7:06 p.m. that servers it had brought back could “become unresponsive again once they receive traffic,” so service may return in fits and starts.
FAQ
Is Outlook down right now?
As of 10:13 p.m. ET on Nov. 12, Microsoft said recovery was only partial and its latest fixes were not working as expected. Check status.cloud.microsoft for the current state.
Why did Outlook go down?
Microsoft says many servers failed automated health checks and became unavailable, which overloaded the rest. It has not named a root cause.
Was the Microsoft outage a cyberattack?
A Microsoft spokesperson told the Guardian and ABC News there was no indication of a cyberattack.
Is Teams down too?
Teams was on Microsoft’s list of affected services. Microsoft also told the BBC that messaging and online meetings were largely working.
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Updated November 13, 2026