Big problem Zoho mail

Hi,
I hope someone can answer this. I have posted in Zoho mail forum but just don't get anywhere.

Hereis the problem:

We want to have our staff using Zoho email accounts but do not want them all to be able to see each others emails.
At the moment when we log onto Zoho email you can select the email account you wish to use from the drop down on the top of the left hand menu.

How do we just set up an email for a new member of staff so they can't then also log into other peoples email and see them?

Just to be clear, we want Paul, Steve and Jane to have a zoho email account each.
The email addresses need to be using our website domain name.

This i swhat the emails would be:

paul@ourcompanyname.com
steve@ourcompanyname.com
jane@ourcompanyname.com

They can all log into the email account and send and recieve email but only from there own account and not other peoples accounts.

How can this be done? How do we set privacy levels? Please do a step by step guide someone. Please don't link me to this Whats New page IT IS NOT THE ANSWER TO THE QUESTION:
http://zohomailhelp.wiki.zoho.com/Configuring-Mail-Accounts.html

Many thanks.

Bob