A widespread Microsoft outage on Thursday, November 12, 2026, left many users unable to send or receive email in Outlook. Microsoft first reported trouble "accessing Exchange Online mailboxes through multiple connection methods in the Americas," then said users in any region could be affected, Forbes Australia reported. The outage also hit Teams, SharePoint, Copilot, and other Microsoft 365 services.

Outage reports for Outlook peaked near 130,000

Problem reports began climbing before 1 p.m. ET. Outage tracker Downdetector showed more than 2,400 reports for Outlook at 12:50 p.m. ET and more than 25,000 by 1:03 p.m., according to GV Wire.

Reports peaked at nearly 130,000 just after 1 p.m. ET, the Associated Press reported. Many users said they couldn't send or receive email, or couldn't load their inboxes at all.

Microsoft's own service status page was also unavailable for a time, GV Wire reported.

Microsoft points to an overloaded process on its own servers

Microsoft confirmed the problem on its Microsoft 365 Status account on X and pointed admins to incident EX1550543 in the Microsoft 365 admin center.

Microsoft said a number of servers were "unexpectedly unavailable" after failing automated checks, according to the AP. Those servers going offline pushed their load onto the rest of the infrastructure. Microsoft ruled out a traffic surge, Forbes Australia reported, and later pointed to a core process on the affected servers that was becoming overwhelmed and causing them to stop responding.

Microsoft paused deployments, rerouted traffic, and restarted servers. Those steps didn't bring the relief it expected.

Recovery hadn't held as of Microsoft's update at 7:06 p.m. ET on November 12. Microsoft said the servers it returned to service "can become unresponsive again once they receive traffic." It was limiting which types of traffic reach the affected servers in some locations and rebuilding a subset of servers using a previous configuration to see if that keeps them running.

More than a third of healthcare IT leaders surveyed use Microsoft 365 for email

Microsoft 365 is the primary email platform for 38% of healthcare IT and security leaders in a Paubox survey of 170 respondents (March 2026). For those organizations, appointment reminders, referrals, and messages between staff and patients run through the service that went down.

A HIPAA contingency plan should cover an email outage

The HIPAA Security Rule requires covered entities to have a contingency plan, including a data backup plan, a disaster recovery plan, and an emergency mode operation plan.

For email, that means knowing in advance:

  • How staff will reach patients and each other if the inbox is down
  • Who confirms the outage and tells staff, before anyone tries a workaround
  • That no one moves patient information to personal email or texting while the outage lasts

Go deeper: What does an email outage mean for your HIPAA contingency plan? and Preparing for an email server downtime

Related: HIPAA compliant email