Microsoft 365 outage MO1550821: Exchange Online, Teams, Intune down, no full fix yet

Microsoft 365 has been partly or wholly unavailable for many customers since about 18:00 UTC on 12 November 2026, and at roughly 05:00 UTC on 13 November the company still had no full fix. Exchange Online (Outlook email), Teams, SharePoint Online, Copilot 365 and Defender were all listed as affected, and so were the admin tools that IT staff use to manage them. This article is a snapshot of what Microsoft and the outlets covering it had confirmed up to that point. It will be updated.

Key points

• The outage began around 18:00 UTC on 12 November 2026 (about 1 pm US Eastern), first as email failures in the Americas, and Microsoft later said it could affect users in any region.
• Microsoft's status page listed Exchange Online, Teams, SharePoint Online, Copilot 365, Defender, Planner, To Do, Intune, Purview and Power BI as possibly affected.
• Microsoft says the extra load came not from more traffic but from a large number of its servers becoming unexpectedly unavailable, and it says it has no indication of a cyberattack.
• Servers Microsoft brought back were reported to become unresponsive again once traffic returned; the latest update we could read said the change it applied was not taking as expected.
• Admins should follow incident IDs EX1550543 and MO1550821 in the Microsoft 365 admin center; there is no patch to install.

What to do

This is a fault inside Microsoft's cloud, so no update, setting or reboot on your side fixes it. There is still work for administrators:

1. Check Service health in the Microsoft 365 admin center and look up the advisories reported for this incident: MO1550821 (the broad advisory covering Exchange Online, Teams, SharePoint Online, Copilot and Defender XDR), EX1550543 (Exchange Online) and TM1550488 (an earlier Teams problem in North America that Microsoft later said was resolved). Those IDs come from news coverage; your tenant's own view is the authority.
2. Expect the admin tools themselves to fail. TechCrunch reported the admin center was unreachable during the outage, and The Register reported that Intune and the Microsoft 365 Apps Admin Center went down too. Microsoft posted updates on its Microsoft 365 Status account on X for people who could not reach the admin center.
3. Confirm it is this incident before troubleshooting locally. If Outlook, Teams or a Copilot feature fails while your network and sign-in are fine, assume Microsoft's side first, and do not make configuration changes that you would have to undo.
4. Tell users which channel to use while email is down: phone, a different chat tool or a status note on your intranet.
5. Check connected AI tools. OpenAI said it was investigating an issue with Microsoft connectors in which new connections may be broken, and Anthropic said an upstream provider issue was affecting its Microsoft 365 connector. Assistants that read mailboxes or SharePoint through those connectors can fail even if your own setup is correct.

Microsoft has not said whether any mail was lost, so do not assume either way; ask senders to resend anything important that bounced once service is stable.

What happened

The Verge dated the first reports to just before 1 pm US Eastern on Thursday 12 November, which is just before 18:00 UTC. People around the world could not open Outlook on the web or in apps. Microsoft acknowledged the issue from its Microsoft 365 Status account, first saying a portion of infrastructure was experiencing "elevated load across multiple regions". Microsoft communications director Ben Hope said the company was investigating "issues with Microsoft 365 services, primarily issues with Exchange Online".

The problem then widened. TechCrunch reported that the company said Teams, SharePoint, Copilot and Defender XDR were unavailable too, and that consumers could not reach OneDrive or Office on the web. Microsoft's status page, as quoted by ABC News, said users may be unable to connect to multiple 365 services, including Exchange Online, Microsoft Teams, SharePoint Online, Copilot 365, Defender, Planner, To Do, Intune, Purview and Power BI.

Microsoft's explanation changed as it learned more. The first message pointed at load. A later one, quoted by ABC, said: "We've determined that the elevated load isn't driven by an overall increase in traffic, but by a large number of servers being unexpectedly unavailable, which is shifting load onto the remaining infrastructure." In other words, capacity dropped, and the servers still working were pushed past what they could handle.

The Register, quoting Microsoft's status page and its X feed, reported two further details. Microsoft blamed "a problem that's causing servers to fail automated health checks and become unavailable", and early investigation suggested the failed health checks "may originate from a specific component that's responsible for processing server health". Later it said "a core process on the affected servers is becoming overwhelmed, which causes the servers to stop responding and contributes to the capacity loss". ABC's account of the same update describes that process as one "responsible for establishing secure connections". The two outlets describe the component differently, and we have not been able to open Microsoft's own incident text to settle which wording is exact.

The recovery attempts

Microsoft's public updates describe a series of steps, none of which had fully worked at the time of the latest reports we could read:

• Early on it paused deployments, shifted connection traffic across its worldwide infrastructure and restarted affected servers (Irish Independent and Reuters, as summarised by WindowsForum).
• Around 22:00 UTC it said it had found and validated an alternative service health check method that let a subset of servers return to service (The Register). ABC reported that Microsoft announced a "gradual recovery" just after 9 am Australian Eastern time, which is about 22:00 UTC, and that an hour later it said restored servers were becoming unresponsive again.
• By 00:35 UTC, The Register said Microsoft reported some servers back online that "initially remain healthy" but "can become unresponsive again once they begin receiving traffic", and that it was analysing diagnostic data to find what triggers this.
• Microsoft also said it was assessing whether reverting a small number of recent configuration updates could help, while also saying it had not found changes to its systems that might have caused the incident (The Register). The status page itself therefore read as somewhat contradictory, as The Register noted.
• The latest ABC update, edited at about 04:46 UTC, said Microsoft's most recent note was that a change applied to improve serviceability "is not taking as expected".

Microsoft has not offered a time for full restoration.

Background

This is not Microsoft's first large Microsoft 365 outage this autumn. TechCrunch noted that the company's last major incident was in September, when a days-long outage hit Microsoft 365 and Microsoft blamed "a core authentication configuration" issue. That makes two big incidents within about two months, with different causes: an authentication configuration in September and server availability in November.

The scale of the dependency is also much larger than it was a few years ago. Organisations use Exchange Online for mail, Teams for calls, Intune to manage laptops and phones, Defender for security alerts and Copilot for AI features, so one regional or platform fault now touches several parts of daily work at once. Admins who run Intune and Defender from the same cloud also lose some of their view into their own estate while the cloud is unwell.

The numbers

The only broad numbers published so far are complaint counts, not Microsoft's own tally of affected customers. ABC reported that reports peaked at about 04:20 Australian Eastern time (about 17:20 UTC) with more than 120,000 users on Downdetector in the US reporting problems with Outlook and more than 45,000 reporting problems with Microsoft 365. Downdetector counts people who chose to report, and many people report whichever Microsoft product they happened to be using, so the figures show how loud the problem was rather than how many accounts failed.

Outlook120000

Microsoft 36545000

Downdetector (US) user reports at the peak, "more than" figures (reports)

	reports
Outlook	120000
Microsoft 365	45000

Source: ABC News (Australia), 13 November 2026

What it means

For administrators, the practical lesson from this incident is about the tools you need during an outage. If the admin center, Intune and the status page are all unreachable at the same time, you need another way to see Microsoft's updates (the Microsoft 365 Status account on X was the fallback this time) and another way to talk to staff.

For governments and large customers, the dependency is visible. ABC reported that Australia's home affairs minister, Tony Burke, said a cyber agreement signed with Microsoft had been activated to make sure Australian interests were prioritised in the restoration, and that the National Cyber Security Coordinator was looking into the outage. In Japan, a deputy chief cabinet secretary said the outage had affected the government's IT infrastructure. The US House of Representatives said its users were affected and its engineers were working with Microsoft. These are the officials' statements as reported by ABC, and we have not seen Microsoft's own accounting of affected government customers.

For AI users, the connector problems are a reminder that assistants which read email and files depend on the same cloud services they sit on top of. When Exchange or SharePoint fails, so do the assistants that rely on them.

What we don't know yet

• The root cause. Microsoft has described symptoms (failed health checks, an overwhelmed core process, servers unavailable) but has not said why servers became unavailable.
• Whether a recent configuration change is involved. Microsoft said it found no changes to its systems that might have caused the incident, yet it also said it was assessing whether to revert recent configuration updates.
• When service will be fully restored, and whether any mail or data was lost.
• How many customers were affected. Downdetector counts are the only public figures we found.

What to watch next

Microsoft normally publishes a post-incident report for major incidents; if it does, the root cause, the time of full recovery and any change to how deployments or health checks work will be there. Watch the Microsoft 365 admin center for MO1550821 and EX1550543, the Microsoft 365 Status account on X, and whether regulators in Australia and elsewhere ask for details. We will add a dated update to this article when Microsoft publishes more.

Sources

• Microsoft 365 Status on X (Microsoft's own updates; we could not read individual posts directly and rely on the outlets below for their wording)
• Microsoft service health status (the public status page, which needs JavaScript and was unreliable during the incident)
• The Register: Microsoft struggling to fix massive cloud outage that's taken down email and Intune
• The Verge: Microsoft Outlook is still down
• TechCrunch: Microsoft's Outlook email hit by new outage
• ABC News (Australia): Microsoft platforms including Outlook suffer widespread outages
• WindowsForum: MO1550821 Microsoft 365 outage guidance (incident IDs and a timeline that cites Reuters, the Irish Independent and BleepingComputer)