A couple years ago, we built a mult-tenant Hosted Exchange 2013 environment for our clients. The environment has one administrator (the domain admin account) which can manage all of the mailboxes, databases, servers, and various other settings in the environment for all of our clients.
We are preparing to migrate to a new Exchange 2016 environment in a new datacenter. One of the things we'd like to change is allowing each of our clients to have their own admin account. This account would ONLY have access to that client. We've tried using Role Based Access Control (RBAC) in the 2013 environment, but we were only partially successful in that the tenant level admin account would still be able to view other client mailboxes.
How do we set up admin accounts for our clients so they can manage themselves but not see anybody else?