I can't believe you are all so trustful. The guy has no credential. He never posted a thing in NXT thread and you believe he has 6-7 millions NXT ? Just so nonsensical.
I am pretty much certain that all big NXT holders have appeared in NXT thread at one point or another. If he is a new guy offering a big amount of NXT, it is more than likely it is a scam.
Yeah, hard to understand why anyone would trust people so blindly.. at least ask for a screenshot or something before trading. Screenshot is usually the easiest way to scare of scammers ("dont know how to take one, cant take it now" etc -> scammer)