Global Microsoft 365 outage: blocked by technical error

A global Microsoft 365 outage blocked emails and work tools for over 20 hours starting November 12, 2026, affecting at least 74 countries. The first reports came in on the evening of November 12. Connectivity issues prevented many users from sending or receiving emails, viewing files, and accessing calendar apps, paralyzing businesses, schools, healthcare systems, and courts worldwide.

What we know

Microsoft confirmed the affected services include Exchange Online, Teams, SharePoint Online, Copilot 365, Microsoft Defender XDR, Planner, To Do, and Intune. The company stated in a press release that this was neither a cyberattack nor an issue related to AI agents. According to the BBC, over 430 million people use Microsoft 365 apps, and the outage caused widespread operational disruptions. Engineers explained that a process on the servers handling secure connections became overloaded. Microsoft restored services gradually, validating stability at each stage, and extended the email timeout window to 48 hours to protect delayed messages.

How it happened

According to official Microsoft communications, the root cause is a technical issue introduced during a previous network capacity update. Professor James Ferryman from the University of Reading told the BBC that when secure connection servers crash, the load shifts to nearby servers, creating an avalanche effect that prevents an immediate restart and requires a gradual recovery. An external analyst noted the outage was not uniform: the issue depends on the server you connect to, not your home country. About 70% of DNS addresses returned errors, while other services remained clean in every region.

Unconfirmed editorial hypothesis: an automatic update or a change to the edge server configuration may have triggered an authentication request loop, saturating the ingress ports and preventing clients from connecting.

Why it matters to your business

When email and shared documents stop, daily operations halt. Security expert Troy Hunt, cited by the BBC, reminded us that Microsoft is a massive part of the internet backbone, and email remains the go-to for appointments, purchases, and service access. If your business lacks a backup plan, every hour of downtime means unpaid invoices, missed appointments, and customers left without confirmations. Relying on a single cloud provider exposes businesses to operational continuity risks that are hard to manage without emergency protocols.

How to protect yourself

• Keep local copies of critical documents and do not rely solely on the cloud for daily operational files.
• Prepare an emergency communication protocol with alternative channels, such as certified email or external mail services.
• Check with your IT department for independent backup systems for network configurations and digital identities.
• Do not attempt to mass-restart company devices during a global outage to avoid worsening server overload.

What we still don't know

Microsoft has not yet published the full post-incident report, which was promised once the reviews are complete. It is unclear how many of the 430 million users were fully affected compared to those who only experienced intermittent issues. It remains to be seen if the email delivery delays caused the permanent loss of any critical communications.