Using older versions of Outlook for Mac for personal email and calendar
Hello,
Microsoft is currently experiencing a widespread outage affecting Exchange Online and several Microsoft 365 services across multiple regions.
Users may have trouble accessing their Exchange Online mailboxes through Outlook on the web, Outlook desktop, and other connection methods. Some features in Teams, OneDrive, OneNote, To Do, and other Microsoft 365 services are also affected.
Microsoft is investigating the issue and working to restore the affected services.
You can check the latest service health status at the link below.
https://status.cloud.microsoft/
Alternatively, you can check the latest updates on Microsoft's Official X (Twitter) account.