You should not need to blank out the Email Subject nor uncheck "Receive a copy", since those are only relevant if an email is actually being sent. Does the email sent actually mention a download, or might you be referring to your Common Thank-you Email that gets sent for every order, regardless of which product(s) the buyer purchases:
Thank you for your purchase. Your Invoice ID is [%invoice%].
Your can view your order details at
You can go to Seller Admin > Account Preferences and edit your Common Thank-you Email, or just delete it to disable that message entirely.
If this does not resolve your concern, please reply to tell us which of your products is the bundled product having the problem.