gmail now has a way to Send mail from another address without "on behalf of".
Instead of using Gmail's servers to send the message, we'll use the servers where your other email address lives. Since Gmail isn't the originating domain, we don't have to include "Sender" info in the header. No more "on behalf of."
http://gmailblog.blogspot.com/2009/0...s-without.html
In some casual testing by me it works with earthlink but not godaddy or namezero. It gets a message:
Your other email provider is responding too slowly. Please try again later, or contact the administrator of your other domain for further information.