Microsoft investigates failed server health checks behind Outlook outage

In a service health update, Microsoft said the failed checks “may originate from a specific component on the affected servers.” The company is testing a targeted change that bypasses the component on some servers and has taken steps to prevent more servers from going offline. It said it had not found a recent change that coincided with the outage and was still investigating why the checks failed.

Microsoft first reported trouble accessing Exchange Online mailboxes in the Americas. Exchange Online stores and delivers email for many Outlook users. The company later warned that the issue could affect Microsoft 365 connectivity in any region. Around 1 p.m. ET, Downdetector showed nearly 130,000 reports of Outlook problems, with users reporting that they could not load inboxes or send and receive email. Copilot users also reported problems.

Earlier Thursday, Microsoft flagged a Teams issue in North America under incident TM1550488. In a follow-up post on X, it said automated recovery systems had started working and were reducing the disruption. Microsoft is posting updates under EX1550543 and MO1550821 in the Microsoft 365 admin center. Users unable to access the admin center can check the company’s public service status page.