Using classic Outlook for Windows in educational settings
Hello BONNEVILLE Dylan,
Good day! Thanks for posting in Microsoft Community. We are happy to help you.
I understand you cannot access your mailbox via Outlook on the web and Outlook app as well. Please correct me if I am wrong.
If I understand correctly, you could access your mailbox before. I have checked the error that you are getting and the reason you cannot access the mailbox is because you do not have a license assigned to your account, as shown by the error “OwaUserHasNoMialboxAndNoLicenseAssignedException”.
To fix this issue kindly contact your Admin/IT department to assign a license to your account.
If you can access Teams as you just mentioned, then they need to check that you have the Exchange Online plan enabled for your license’s apps. For their reference, please follow these instructions: log into Microsoft 365 Admin Center > Users > Active Users > select the user in question > Licenses and apps.
We look forward to hearing from you; Please understand that our initial reply may not always immediately resolve the issue. However, with your help and more detailed information, we can work together to find a solution. Thank you for your cooperation.
Sincerely,
Simbarashe | Microsoft Community Moderator