Microsoft called the recovery “encouraging” on Friday. Service availability and email delivery are improving across a growing portion of the Microsoft 365 infrastructure hit by Thursday’s outage, the company said.
Some users may still hit intermittent problems while the recovery work continues, the company said. The remaining work is twofold, Microsoft said: finish recovering the environments still affected, and clear the email queues and backlog the failure left behind.
The extended 48-hour email timeout window stays in place to protect delayed messages while delivery catches up, Microsoft said.
How the outage unfolded
It began on Thursday in the Americas, where Exchange Online mailboxes would not open through Outlook on the web, the Messaging API, Exchange ActiveSync or the REST API. Microsoft tracked the mailbox failures as incident EX1550543 and later opened MO1550821 for Microsoft 365 connectivity more broadly.
Reports on Downdetector neared 130,000 for Outlook at their peak, and the disruption spread beyond email to Teams, SharePoint Online, Microsoft Copilot and Microsoft Defender XDR. Overnight, Microsoft said servers returned to service could become unresponsive again once they received traffic. The company has given no cause for the outage.
Microsoft pointed administrators to the fuller update under MO1550821 in the Microsoft 365 admin center, or at status.cloud.microsoft if the admin center is not available to them.
Also Read: Update: Microsoft 365 Recovery Progressing in Asia Pacific