Instead of forcing customers to wait for an email, present an instant download link to customers as soon as they complete the checkout process.
Although you can deliver digital goods with IPN [Hack #71] , there might be times you want to allow customers instant access to their purchases with a return page (via PDT). Email messages can be lost, might bounce, or might not be desired at the same address used in the buyer’s PayPal account. PayPal provides a way to redirect your customers back to your web page after they have completed a purchase with PayPal. This return page can be used as another means to provide a data file to your customers and can be quicker than waiting for the email to arrive.