Mailboxes are not showing in the Mailboxes tab after accounts have been discovered (4369991)

This issue may occur due to one or more of the following causes:

• The account is not "mailbox-enabled."
• The mailbox is not stored in the cloud (e.g., in a hybrid configuration).

To resolve the issue, verify the following:

1. Check if the account has a mailbox:
   
   Ensure the account is mailbox-enabled.
   
   

2. Verify mailbox location:
   
   Confirm that the mailbox is stored in Microsoft 365 (Exchange Online) and not in an on-premises Exchange environment.
   
   

3. Validate account licensing and provisioning:
   
   

   • Open the Microsoft Admin Center.
   • Navigate to Users > Active Users.
   • Verify that the account has the necessary Microsoft licenses assigned.
   • In the Mail tab, confirm that the mailbox is properly provisioned.