Only ask the customer's e-mail if his order's total cost is 0$

[matduke]

My shop contains both free and purchasable downloadable products.

I don't want to force customers being on the site solely for free products to make a complete account to get their goods. I only want to collect their e-mail address to send the download link and put them on my newsletter.

Is there a function or free module that sends customers with an order worth $0 to a simple e-mail address form with no complete registration needed?

Thanks in advance!