Hi @Chong
I tested in my lab and seemed to have reproduced this issue.
I suppose the cause of this issue is the attribute msExchDelegateListLink which is responsible for automapping, was not migrated either by the Prepare-MoveRequest.ps1 script or ADMT.
Thus the shared mailbox cannot be automapped in Outlook.
But as a workaround, you should be able to add it manually in Outlook:
- locate File>Account Settings>Change>More Settings>Advanced
- add the shared mailbox as an additional mailbox
You may also remove and re-add the permission to have the attribute added to the account.
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