500 Bonus United Miles after Joining and Activating e-Miles account by 3/31/2014

I am surprised to receive a promotional email arrived today from e-Miles:  500 (400 + 100) Bonus United Miles.  The promotion seems to be accessible via this URL.

"Terms" says more about the definition of "account activation".

Terms

To be eligible for the 400 MileagePlus® award miles, you must activate youre-Miles account before midnight on 3/31/2014. To activate your e-Miles account you must read and respond to six (6) third party offers.* After activating youre-Miles account, your United MileagePlus award miles will be automatically deposited into your MileagePlus account. 

This offer is for new e-Miles members only. Membership is only available to residents of the United States and its territories. If you live outside of these regions and have received this email, we apologize for any inconvenience. 

*e-Miles profile survey offers do not count toward account activation.

A regular 250 bonus United Miles from e-Miles is also available.

Update: 2/27/2014
Argh!  I realized I had joined e-Miles in the past.  After responding to more than 6 third-party offers, I have earned only 270 e-miles.  Minimum redemption requirement to United Miles is 500 e-miles.