Microsoft 365 Outage Passes 9 Hours. Microsoft Still Hasn’t Named a Cause

If Outlook, Teams or Copilot has been flaky or dead for you today, it is not your Wi-Fi. Microsoft’s own advisory MO1550821 puts the start of a multi-service Microsoft 365 outage at 10:26 AM PT (1:26 PM ET) on Thursday, November 12, 2026, and in its 7:48 PM PT update Microsoft was still working on the problem. It has not named a root cause.

Status as of Microsoft’s 7:48 PM PT post. This story is still developing, so check status.cloud.microsoft for the latest.

What Microsoft says is affected

The admin notice first listed Exchange Online, Microsoft Teams, SharePoint Online, Microsoft 365 Copilot and Microsoft Defender XDR. According to the update log ENow Software published, Microsoft added more through the afternoon, including Planner, To Do, Purview, Intune, Defender for Office 365, Power BI and Universal Print. IBTimes also lists consumer services such as Outlook.com, OneDrive and OneNote.

A separate Exchange Online incident, EX1550543, began earlier, at an estimated 8:17 AM PT (11:17 AM ET). It covered mailbox connections through Outlook on the web, MAPI, Exchange ActiveSync and the REST API. A Teams incident from the morning, TM1550488, was resolved by 10:53 AM ET, and Microsoft has not said whether it is related.

On scale, IBTimes cites CNBC for about 130,000 Outlook problem reports on Downdetector at the peak. Security Affairs reports more than 97,000 at 2:07 PM ET. Downdetector counts reports, not affected customers, so treat both as a sign of scale rather than a headcount.

What Microsoft has said about the cause

The explanation has shifted during the day, and it is still incomplete:

• Morning: Microsoft pointed to “elevated load across multiple regions.”
• Late morning: it said the load was not driven by more traffic. Instead, a large number of servers became unexpectedly unavailable and the rest carried the strain.
• Midday: Microsoft said servers were failing automated health checks, paused deployments and configuration changes, and tried a workaround on some servers.
• Afternoon: it said a core process on the affected servers was becoming overwhelmed, causing them to stop responding. It began returning some servers to service, then said servers became unresponsive again once traffic reached them, so it was limiting some traffic types and rebuilding some servers on a previous software configuration, per the ENow log.
• Evening: in its 7:48 PM PT post, Microsoft said it was reviewing traffic flows and affected infrastructure to find ways to improve routing, after “sustained traffic management imbalances.”

Per IBTimes, Microsoft said it had found no recent change that matched the start of the outage, while it assessed whether reverting some configuration updates could help. MLQ reports that SecurityWeek found no disclosed evidence of a cyberattack. Neither is a finding. Microsoft has not said what caused the servers to fail.

AI tools felt it too

Security Affairs reports that OpenAI said new connections to Microsoft services might fail and some tools might not work properly, and that Anthropic said its Microsoft 365 connector was affected by a problem at an upstream provider. If you use an AI assistant wired into Outlook, Teams or SharePoint, that is the likely reason it is misbehaving today.

What to do if you are affected

• Check status.cloud.microsoft or @MSFT365Status first. Admins can read MO1550821 and EX1550543 in the Microsoft 365 admin center.
• Microsoft’s updates describe a server-side problem, so reinstalling Outlook or resetting your password is unlikely to help.
• For anything time-sensitive, use another channel such as a phone call or text, and do not assume an email you sent today arrived. Microsoft says users may see a gradual recovery as capacity returns.

PCGeek’s take

Outages happen. What stands out here is the length and the spread: more than nine hours since Microsoft’s advisory start, a long list of services, and a fix that has not held, with restored servers failing again under traffic. When one infrastructure fault can knock out mail, chat, meetings, security tools and AI assistants together, the real risk is how many of your tools sit behind the same door. A backup way to reach your team is cheap insurance.

What we could and could not confirm

We confirmed the outage through Microsoft’s own status account, the update log for MO1550821 and EX1550543, and several outlets. We could not confirm a root cause, because Microsoft has not given one, or a time for full recovery. Posts on X calling it a “24-hour outage” or quoting a statement from CEO Satya Nadella were not backed by anything we could find, and we left them out. Times above come from Microsoft’s updates as reported by the sources linked in this story.

Did Outlook or Teams stop working for you today? Tell us what you saw in the comments.

Follow @pcgeekinfo for updates as Microsoft says more.