Outlook mailboxes that run on Microsoft’s Exchange Online service started failing on Thursday evening, 12 November, and Microsoft’s last update we could read, at 00:31 PKT on 13 November, says engineers are still bringing servers back into service. The situation remains unchanged at the time of writing
Microsoft’s Microsoft 365 Status account posted about the problem at 22:54 PKT (17:54 UTC), saying users in the Americas could not reach Exchange Online mailboxes through several connection methods.
Microsoft’s explanation changed during the evening. By 23:35 PKT Microsoft blamed heavy load on part of its infrastructure, spread over several regions, for the connection errors. Then, at 00:31 PKT, it revised the diagnosis. Traffic had not grown; instead several servers had dropped out without warning, and the ones left running were carrying their share. Microsoft says it is working to return them to service safely. It gives no time for a fix and has not named what took the servers offline.
The incident is tracked in the Microsoft 365 admin center as EX1550543, with a second record, MO1550821, covering the wider Microsoft 365 effect. Microsoft also told administrators to read updates at status.cloud.microsoft if the admin center itself will not open for them. The Microsoft 365 Status account carries the newest word.
Microsoft’s posts name two services. Exchange Online is the one that carries Outlook mail and calendar. Teams had its own, separate incident earlier on 12 November: at 20:40 PKT (15:40 UTC) Microsoft said it was investigating problems using Teams in North America, under TM1550488. We did not find a later Microsoft update on that one, so we cannot say if it is fixed.
Some users have also reported trouble with Copilot, but Microsoft’s posts do not list it. Azure’s public status page, which only covers widespread incidents, showed no problem when we checked.
Microsoft’s posts give no workaround for the mailbox problem, so affected users can only wait for the servers to return.
