In my emails over the weekend, I received an offer from American Express for a $25 credit to my account if I spent $75 on Amazon with my American Express card. My understanding is that this needed to be in one order, though the email wasn't explicit. The email was explicit that you had to click on a link in the email to activate the offer. I wasn't sure I would have something to spend that much money in one order, but the deal on the Fire HDX solved that problem for me!
If you have an AE card, look for this email and click on the link to activate it! I have a Delta Airlines branded affinity card, but I didn't see anything in the email limiting it to that style of card.
