There's a rule of thumb that the longer the form, the less likely people are to fill it out. But in your case, you're asking for the information in order to serve the customers' needs. I suggest you tell customers that if they register once they won't have to put in their delivery information each time they order. Promise to save them time--increase convenience--and most will be happy to comply. It's unlikely customers will believe you really need their email addresses, except perhaps for future promotion, so to obtain this you might offer a reward, such as a coupon for first time registrations.