Error 500 occurs in Outlook.

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Hi dongwoo lee

Based on your description, it looks like the issue may be related to the Outlook client rather than the mail server, since emails are still accessible via webmail. 

As a quick troubleshooting step, could you please try creating a new Outlook profile and check if the issue persists? 

Here are the steps: 

• Go to Control Panel > Mail > Show Profiles  
• Click Add to create a new profile  
• Add your email account again  
• Set the new profile as default, then open Outlook  

Reference: Create an Outlook profile - Microsoft Support 

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. Please let me know how it goes. 

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The error message indicates that Outlook on the web (OWA) is returning HTTP 500 with OwaUserHasNoMailboxAndNoLicenseAssignedException and UserHasNoMailboxAndNoLicenseAssignedError. This means the signed-in account currently has no active Exchange Online mailbox or no valid Exchange license assigned, so Outlook cannot load the mailbox.

Because the mailbox and licensing state are controlled in the tenant, resolution requires action by the Microsoft 365/Exchange Online administrator:

1. Contact the tenant administrator
   • Ask the Microsoft 365 (Entra ID/Exchange Online) administrator to check the account.
2. Verify mailbox status in Exchange Online
   • The admin should check whether the user has an Exchange Online mailbox and whether it is disabled or removed.
   • If the mailbox is disabled or treated as terminated, it must be re-enabled or recreated for the user.
3. Verify license assignment
   • The admin must ensure an appropriate license that includes Exchange Online is assigned to the user.
   • After assigning or correcting the license, wait for directory and service replication, then sign out and sign back in to Outlook on the web and Outlook desktop.
4. Retry Outlook
   • After the mailbox is active and licensed, restart Outlook desktop and try Send/Receive again.

If the problem persists even after the admin confirms that the mailbox is enabled and properly licensed, the admin should continue troubleshooting in Exchange Online, as the error is being generated on the server side rather than by the Outlook client.

References:

• Not able to have access to my email ! - Microsoft Q&A