After a migration to Office 365 hybrid environment, delegates or managers are moved to Exchange Online. However, the delegates are listed two times in the Delegates dialog box in Outlook.
When you view the permissions, a value of None is listed in the Delegate Permissions dialog box.
Note In some cases, the delegate is listed only one time, but the permissions are still listed as None.
However, when you view the calendar or other folder properties in Outlook, the appropriate permissions are listed.
Also, an administrator can view permissions in Exchange Remote PowerShell by using one of the following commands:
Delegates can still send on behalf of others as expected. This is true so long as they are listed in the Delegate Permissions dialog box. This can be verified by an administrator by running the following command from the Exchange Online environment:
Get-MailUser ManagerSMTP | ft GrantSendOnBehalfTo
Additionally, delegates report that they cannot see private items if they were previously granted this permission.
This issue is currently under investigation by Microsoft.
No action is required unless delegates require access to private items on the calendar. Delegates retain the access that was granted to their account before their account or their manager's account was migrated. If changes must be made before users have mailboxes in Exchange Online, the folder permissions can be managed from the folder properties. The permissions can also be reapplied in the Delegate Permissions dialog box.
Note If the delegate is listed two times in the Delegate Permissions dialog box, you do not have to remove the duplicate user unless the delegate has to be able to view the private items. If you make any change, you should take steps to reconfigure the delegate fully. To do this, you must re-add the folder level permissions in Outlook, and select the Delegate can see my private items check box.