Using classic Outlook for Windows in business environments
Update: Microsoft just updated there is an ongoing incident at the moment. This affect multiple Microsoft 365 services.
Microsoft 365 Service Update – MO1550821 (This link required admin role to access)
Microsoft is continuing to investigate connectivity issues affecting multiple Microsoft 365 services. The engineering teams have identified elevated infrastructure load across several regions and are actively working to restore service capacity.
Hello @June Wu
I'm sorry for the inconvenience this issue has caused.
Multiple users have also reported similar issues accessing their Microsoft 365 mailboxes through both the Outlook desktop application and Outlook on the web.
This may indicate a service-side issue rather than a problem with your individual account or device.
Please be patient while Microsoft investigates and works toward resolving the issue.
If Microsoft publishes any official updates or announcements regarding this incident, I will update you as soon as possible. In the meantime, you can also monitor the Microsoft 365 Service Health dashboard for the latest information:
https://admin.microsoft.com/#/servicehealth
Thank you for your understanding and patience.