One of my items is a downloadable MP3. The user has the choice to order a hard copy of the album or download it. If they select to download the item, how can I redirect them to the URL or email them a link to download the .mp3. Not all notification emails should include the download url (if they've requested a hard copy).
If possible, I'd like to limit them to one download so they can't just share the url with other people.