I have had the same offer as NEJ1941, from that same address and also from email@example.com, dressed up as a Norton ASdvantage newsletter.
It seems like a (very astute, but plausible) scam to me.
I have advised Norton of this separately.
It would be most helpful if Norton could comment generally on the "offer", as to whether it is genuine or not.
Digital River is a legitimate Symantec reseller. You may visit the their website (http://shop.symantecstore.com) for product information & pricing. You may call them at 1-877-200-2307 for more information about the offer.
Hope that helps.
Enterprise Customer Care