I sell tangible products, and I don't want a thank you email to be generated by e-junkie. I've created a few one cent test buttons, and I get a thank you email regardless of how I configure them. If I check 'enable templated email' and leave the email message section blank, I get a thank you email. If I leave the box unchecked I get an email.
Under Product Configuration, I have 'shipping/buyer's address' checked and 'Let buyers edit quantity in cart' checked. Don't know if this would make a difference.