Ideally, we would be able to limit people to view, edit and communicate with messages in the shared inbox based on the same "All, Team-Only, Owned-Only, None" degrees. This would be similar to the access granted on all other standard objects.
I, as a Solutions Partner, may need to get into a portal to set up shared inboxes snd channels for a client, but for security purposes, should not be able to see actual client data and interactions. Without limiting my access but not shutting off my Account Access, this is not possible.