https://www.optoutprescreen.com/?rf=t
For US citizens...This is the official website to opt-out of getting credit or insurance offers in the US mail. It is seperate from the opt-out for phone-call solicitations. You can choose to be free of mail for five years or permantently, If you do not want to use the internet to enter your information, you can also call the phone number that they provide on the website to do the same thing. Just for a side-note, you can also reactivate your mailings on the same page, or same phone number if you decide you like that sorta thing.