we are the italian partner of Zoho, we haeve a problem with one our costumer, 

i manage and setup the campaign with admin user, now i need to let another user to acces to the campaign, but when i try to add i receive the error:

This email address has been already used in some other organization. So you cannot add/invite this user.

The email is marketing AT kairos-consulting.com 

Let me know how i can do..

thanks!

Federico