all e-mail viewable by all users

[semperfried76]

I need mailboxes to be private unless explicitely shared (or archived), instead, all e-mails are viewable by all users, even those without administrator access. Is there a way I can change the permissions so that these e-mails are not viewable by all users?

[sanjaykatiyar1]

You can define the Roles and assign users to the role.
In the role you can specify the various access levels.