Using Zoho Mail in Zoho CRM...

Using Zoho Mail in Zoho CRM...

 I need to set up different email addresses in Zoho Mail because I have email addresses from the companies that I provide services for.  How do I do a mass email using one of my other email addresses?  When I go to select which email to use...it only shows my company email and the other users for our company.  The other email addresses are not on the selection list.

David