Question about options for sharing emails in Zoho

Question about options for sharing emails in Zoho

Hi everyone, just wondering if this is possible.  I think sharing emails is incredibly handy, but I don't like my reps being able to see each others emails.  Is there any way that I can have a role so that my users emails are shared in Zoho but only to themselves PLUS myself as a manager?  Or is it owner or no one at all?

Secondly if I choose the option to only share emails when I choose the option to do so, is there any way to make the sharing ON by default requiring the user to disable it?  If not, just to confirm, mail in Zoho mail that is archived etc is always there right?  So if a user forgets to check the "Share emails" button, they can go in at a future time and check it, and the emails will appear correct?  Not just future ones?  Thanks!