Offer coupon for registration

I am trying to collect as many visitor emails as possible without gating my site.  I wanted to offer a virtual coupon tied to a user email address in exchange for registering and signing up for our newsletter.  I am a software engineer and have chops if necessary to accomplish the task.  I was looking for thoughts on how to do this.  Could I just hook up into a "Thank You for Registering Email" to distribute coupon?  Where would I validate that it is the correct coupon when they go to use it?  Any thoughts on incetivizing registration would be appreciated.

Out of the box you can offer reward points for registering and soon for newsletter subscription.
https://www.nopcommerce.com/boards/t/18705/suggestion-a-simple-way-to-generate-massive-and-personalized-discount-coupons.aspx