Microsoft is investigating a widespread service issue causing authentication issues and email delays and failures for Exchange Online customers. [...]

https://www.bleepingcomputer.com/news/microsoft/microsoft-exchange-online-outage-causes-email-failures-auth-issues/

Microsoft is investigating a widespread service issue causing authentication issues, email delays and failures, and various other issues for Exchange Online customers. [...]

https://www.bleepingcomputer.com/news/microsoft/microsoft-exchange-online-outage-causes-email-failures-auth-issues/