I have read the T&C for communicating with Amazon.com customers after the purchase and there was a bit about how you may be able to contact them "per your agreement only". Mostly, it sounds like you can only communicate regarding a purchase or a question about shipping.
So has anyone arranged any sort of contract for marketing to amazon.com customers after they buy from you?
or
Are you communicating in any other way to an Amazon customer after they buy from you?