To remove and re-add a user’s mailbox permissions using PowerShell, we can use the following steps. Also, this will need to be performed using PowerShell, because the Exchange Admin Center doesn’t expose the option to enable or disable auto-mapping when configuring mailbox permissions. If you want to remove auto-mapping for a user’s access to a shared mailbox, then you must remove their mailbox permissions and then re-add the permissions again. The auto-mapping option can only be configured at the time the permissions are granted. When auto-mapping is enabled, Outlook receives extra information in the Autodiscover response that tells it to open the additional mailbox. The reason that the shared mailbox appears in Outlook, but does not appear in the Outlook account settings, is that auto-mapping is enabled by default when a user is granted access to a shared mailbox or to another user’s mailbox. In the Outlook account settings for the user, the shared mailbox does not appear as an additional mailbox. This can occur for on-premises Exchange Server and cloud-hosted mailboxes in Exchange Online. Although this case was for shared mailboxes, the cause and solution apply equally to user mailboxes. In this case they were shared mailboxes and appeared in the left pane of Outlook. A customer asked about a situation in which they’re unable to remove mailboxes from users’ Outlook profiles.
