Are you serious? That's a huge waste of time and effort.
There is a phone number you can call where you can opt out of receiving heavy volumes of junk mail and pre-screened credit offers, similar to the "do not call" telemarketer listing.
I did it about three months ago and I've noticed a significant drop in the crap mail I get. I suggest you do the same.
Plus some poor sap in the mail room of whatever company you're sending that crap to has to deal with your mail.
EDIT:
https://www.optoutprescreen.com/?rf=t. Check out this website. Looks legit, though I would completely investigate before sending them personal information.
Also, if you take a look at the very bottom of the next credit card offer you receive, there should be a 1-888 number on it. Be sure to call that number to opt out of all credit card prescreens.