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How to Fix Exchange Admin Center 'Failed to Get Mailbox Permissions' Error
Question details
Users need to resolve an issue where the Exchange Admin Center fails to load mailbox permissions after assigning access to an Azure service principal.
- Product
- Microsoft Exchange Online
- Device & OS
- not provided
- Scenario
- An administrator is attempting to view or manage mailbox delegations in the Exchange Admin Center after assigning mailbox access to an Azure application.
- Observed behavior
- The Exchange Admin Center throws a 'Failed to get mailbox permissions' error, blocking visibility of delegations for both user and shared mailboxes.
Ensure you have Exchange Administrator or Global Administrator privileges in your Microsoft 365 tenant and that you have installed the Exchange Online PowerShell module.
Recreate the Service Principal with a Display Name
The error is triggered when an assigned service principal lacks a display name. Recreating it properly via PowerShell resolves the interface error.
While service principals might still not appear directly in the Exchange admin center delegation list, giving them a display name acts as an effective workaround to stop the error from breaking the permissions view.
Open PowerShell as an administrator and connect to your Exchange Online environment using your administrative credentials.
Remove the existing problematic delegation and delete the service principal that lacks a display name.
Run the command: `New-ServicePrincipal -AppId <AppId> -ServiceId <ObjectId> -DisplayName "EXO Service Principal for Azure AD App"` to properly recreate the principal.
Retrieve the principal using `Get-ServicePrincipal`, then assign FullAccess to the mailbox using the `Add-MailboxPermission` cmdlet.
Log back into the Exchange Admin Center, navigate to the mailbox delegation settings, and verify that the permissions view loads without the error.
Remove the Application Delegation
If the service principal is no longer required, simply removing its delegation entirely will instantly restore the mailbox permissions view.
Open a Microsoft Support Ticket
If PowerShell modifications do not resolve the error, the tenant backend may require direct investigation by Microsoft Support.
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Frequently Asked Questions
Why do I see 'Failed to get mailbox permissions' in Exchange Admin Center?
This error typically occurs when an Azure service principal is assigned mailbox access but lacks a defined display name. The missing attribute prevents the Exchange Admin Center from correctly rendering the permissions list.
Will fixing this error make the service principal visible in the delegation list?
No, service principals generally do not appear in the Exchange admin center delegation list even after a fix. However, recreating it with a display name acts as an effective workaround that stops the error from blocking your view of other user delegations.
Does this issue affect both user and shared mailboxes?
Yes, the permission error can be triggered on both user mailboxes and shared mailboxes whenever a problematic application delegation is attached to them.
