Mail hosting: How to remove "user@zoho.com on behalf of user@domain.com"

Mail hosting: How to remove "user@zoho.com on behalf of user@domain.com"

I have successfully configured mail hosting, but my messages are being sent from

johnsdr@zoho.com; on behalf of; <me@mydomain.com>

Is it possible to change my default user?

Do I need to add another user account and delete the zoho.com account?