CRM email plugin

We are launching a large Zoho implementation next week and I have two questions. From what we've discovered if you delete or archive an email that is logged in a contact history the email disappears from the contact history. Is there any way to correct this? For a business like ours we need to make sure our emails in the contact history are there in the future in the event of any legal situation with the customer. Also when we terminate an employee and deactivate their Zoho account from the CRM and close their account, what happens to the emails logged by that user in a contact history?