In Exchange Server 2010 SP1, shared mailbox with full access rights will be auto mapped to the users given such rights. This is fine for that user who doesn’t seem to know how to add an additional mailbox to their Outlook 2007, 2010, 2013 client. But what about those support and systems admins who grant themselves access for troubleshooting and find out later they are stuck with this new folder under their Outlook folder that can’t be removed.

Well we never say “can’t”. So what you need to do to remote the auto-mapping attribute is to reach out to the administrator if you are not one or if you are just find your way to the Exchange Management Power Shell and issue the following command:

Add-MailboxPermission -Identity <shared mailbox alias> -User <your mailbox alias> -AccessRights FullAccess -InheritanceType All -Automapping $false

Once this command is run the additional mailbox will automatically be removed.

Reference: Disable Outlook Auto-Mapping with Full Access