 <p>You can't send through the email submitted on the form, since you aren't authorized to use that email. You either have to use an email you control or the user's email by connecting to their Google account. <a href="http://code.google.com/appengine/docs/python/mail/sendingmail.html" rel="nofollow">http://code.google.com/appengine/docs/python/mail/sendingmail.html</a> This page says which email you can use to send emails from, just scroll down right after the first code block.</p>