Just got this email, no need to register, but I guess it is targeted at accounts that have stagnated a while, in my case my last MP dine was 4/12.
Your account has been hibernating lately, but you're going to want to wake it up before winter hits. It's time to stock up on miles, and to make sure you're well supplied, we're giving away double on every dine September 11–25. (See below for details.)
You don't even need to register—just dine!