I read this sentence about unsolicited credit card offers and laughed “Opting In: Most consumers prefer to continue to receive offers that may interest them.” (source: http://www.experian.com/credit-education/opting-out.html)

Do people really sign up for credit cards offers they receive unsolicited? Either way, an effective way to control what direct mail you receive (as best as you can, nothing will ever stop it) for five year periods is to register with DMA Choice.org: https://www.dmachoice.org/dma/member/home.action

They have a pretty good tutorial on the hows and whys of direct mailing as well which I found interesting: https://www.dmachoice.org/dma/static/learn_more.jsp