What MS has posted so far:
>> Microsoft 365 Status >> @MSFT365Status >> We're investigating reports of users experiencing issues accessing Exchange Online mailboxes through multiple connection methods in the Americas. More details can be found in the Microsoft 365 admin center under EX1550543. 12:54 PM · Nov 12, 2026
>> Microsoft 365 Status >> @MSFT365Status >> While we're working to mitigate impact, we've confirmed the issue may affect Microsoft 365 service connectivity for users in any region, more information will be provided in the Microsoft 365 admin center under EX1550543.
>> Microsoft 365 Status >> @MSFT365Status >> We've determined a portion of infrastructure is experiencing elevated load across multiple regions, which is likely contributing to the connectivity errors. We're providing more information under EX1550543 and MO1550821 in the Microsoft 365 admin center, as well as https://status.cloud.microsoft
>> Microsoft 365 Status >> @MSFT365Status >> 20m >> We've begun redistributing connection traffic across our broader worldwide infrastructure to help balance the load. More info under EX1550543 and MO1550821 in the Microsoft 365 admin center, as well as https://status.cloud.microsoft if the admin center is not available to you.
The biggest site I work for, who went M365 hybrid last year, has incurred more Exchange downtime today than they had all of last year with their on-prem Exchange servers.