Global Microsoft 365 outage: what happened and how to protect your business

Since late afternoon on Thursday, November 12, 2026 (Central European Time), a worldwide outage has been disrupting Microsoft 365. At the heart of the incident is Exchange Online, the service behind business email in Outlook. Here is what we know so far, and what your teams should do.

Written on Friday, November 13, 2026, late morning. The situation is still evolving: check the official service status (link at the end of this article).

What happened

The first reports appeared on Thursday afternoon. Microsoft initially described problems accessing Exchange Online mailboxes in the Americas, then confirmed that users in any region could be affected. Within about an hour, the outage tracker Downdetector was receiving reports from 74 countries and territories; in the United States, Outlook alone peaked at more than 130,000 reports.

Government services were affected in Singapore, Japan and Australia, along with third-party tools that connect to Microsoft 365, such as the OpenAI and Anthropic connectors.

Affected services

• Outlook (web, desktop and mobile): mailboxes unavailable or very slow, and delayed email delivery.
• Teams: calendar and email-related features disrupted. Chats and calls largely kept working.
• Copilot, SharePoint Online and other services that rely on Exchange Online data.
• On the consumer side, Outlook.com, OneDrive and the web versions of the apps were also disrupted.

Microsoft is tracking the incident as EX1550543 (Exchange Online mailbox access) and MO1550821 (impact on other Microsoft 365 services).

What caused it?

No root cause has been published yet. Microsoft described unusually high load across several regions: servers that had become unavailable were failing their automated health checks, pushing traffic onto the rest of the infrastructure, which then became overloaded in turn. The company stressed that this load was not caused by an increase in user traffic.

To regain control, Microsoft paused deployments, restarted servers, rebalanced traffic and rolled back a recent network configuration change, without saying that this change caused the outage. On Friday morning, a fix applied to an authentication and routing component was showing encouraging results and was being extended region by region. Microsoft says it has found no sign of malicious activity and plans to publish a detailed report once the incident is closed.

Why recovery is taking so long

Each server brought back online was immediately hit by every pending connection, became overloaded and failed again: a classic domino effect in very large infrastructures. That is why service is coming back gradually, region by region, and why some apps take several minutes to reconnect.

What to do during the outage

• Do not reinstall Outlook or delete profiles and accounts: the problem is on Microsoft’s side, not on your devices. These steps would force a full resynchronisation later.
• Follow the official source: the Microsoft 365 admin center (incidents EX1550543 and MO1550821), or the public service status page if the admin center does not respond.
• Let clients and partners know through another channel (website, social media, a call) that your replies may be delayed.
• Use the tools that still work: Teams chat and calls remained largely available.
• Once service is restored, check that important emails sent during the outage actually arrived.

Lessons for businesses

The cloud remains highly reliable day to day, but no provider is immune to a major incident. A few simple measures greatly reduce the impact on your business:

• A written continuity plan: who alerts whom, through which channel, and which tasks can continue without email.
• An independent Microsoft 365 backup (email, OneDrive, SharePoint, Teams) so you stay in control of your data.
• Service health alerts set up in the admin center, so you are informed within the first minutes.
• A backup channel to reach your teams and clients.
• Offline mode in Outlook and OneDrive: emails and files that are already synced remain available.

Sources

• Al Jazeera – Microsoft hit by global outages: what happened and why? (13 Nov 2026)
• CNBC – Widespread Microsoft outage takes down Outlook and other 365 services (12 Nov 2026)
• The Register – Microsoft’s massive M365 outage stretches past 12 hours (13 Nov 2026)
• UC Today – Microsoft 365 outage: Outlook down, and the fix won’t hold (13 Nov 2026)
• Official Microsoft 365 service status

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