Microsoft probes Exchange Online outage hitting Outlook users

Microsoft is investigating an outage that has left users unable to reach their Exchange Online mailboxes, the email service behind Outlook at companies and schools. The Microsoft 365 status account acknowledged the problem on Thursday and pointed customers to incident EX1550543 in the admin center.

The first notice described trouble across several connection methods in the Americas. Microsoft later said the problem could affect Microsoft 365 connections in any region.

For now, the company points only to overloaded infrastructure in several regions, and it is moving connection traffic to the rest of its global network to spread the load. It has not confirmed a root cause, and it has not tied the outage to a cyberattack.

Anyone who relies on Outlook for work may have email that will not send or arrive while the incident lasts. Teams, SharePoint Online and Copilot are listed as potentially affected, but Microsoft has not said how badly, and it is not confirmed that they are failing for every user. Nor has the company said whether users in Mexico are hit in particular: its notice refers only to "the Americas."

Microsoft 365 administrators can follow updates under EX1550543 in the Service health section of the admin center. The company has not given an end time.