I bought that very same Mitsouko, fulfilled by Amazon, with free Super Saver Shipping just this past May.
Mine is definitely real, most likely gray market. The code on the bottle matched the box and I verified the code on checkcosmetic.net.
This is my first bottle of Mitsouko after having originally tested it via a decant from The Perfumed Court. The longevity is great and I'm very pleased with it.
I hope this information is useful to you and good luck!