After a migration to Microsoft Office 365, users cannot open a folder or add a hidden mailbox in Outlook. Also, users may receive the following error messages, depending on what they are trying to add or access.
- Additional mailbox
The name cannot be resolved. The name cannot be matched to a name in the address list.
- Additional Exchange account
The name cannot be matched to a name in the address list.
- Calendar or other folders
Microsoft Outlook does not recognize UserName.
This is expected behavior when you try to add a hidden mailbox.
If you migrate from a legacy dedicated environment to Office 365, you will have to work with Microsoft Support. To do this, follow these steps:
- As an administrator, grant Full Access permissions to the hidden mailbox.
- Contact Microsoft Support to request that they add the msExchDelegateListLink attribute manually in the legacy dedicated environment. Microsoft Managed Services Service Provisioning Provider (MMSSPP) will write back the value to the legacy dedicated environment. This attribute value will then be synchronized to Office 365 by using Azure Active Directory (AD) Connect.
Note It may take several hours for the appropriate values to be synchronized fully and found by Autodiscover to add the hidden mailbox to the user's profile.