I did some searching. From what I can see its a marketing PR stunt for a company. It appears they purchased a mailing list from a third party and sent out a huge amount of these coupons to people on this purchased mailing.
The catch seems to come when an online purchase is made and the shipping fee jumps from free to $10.
So basically anyone who go these coupons, at some time in the past signed up to X company to receive coupons etc in the mail. X company has then sold this list of names and addresses to the people doing marketing for Jenny B.