Secure emails only to case 2016 On prem

We are embarking on case management in CRM 201 on premise and plan to automatically create cases from emails send to a particular email address.  However, for one of our groups that wants to use case management, they do not want the emails that were used to create these cases to be available to anyone else in the organization.  Is there a way to stop these emails from being automatically related to the account/contact, etc and only available on the case (which is secured by business unit)?  Thank you for any responses!