Once you’ve registered thru Direct Marketing Association as someone who does not want to receive unsolicited direct mail, and you’ve politely called the individual business to ask to not receive mailings or faxed mostly black background notice to remove from mailing list and you are still getting the mail with the excuses: “It’s handled by someone else and I’ve told them to remove you from the list”, “these get printed up months in advance and can’t be stopped”, “just throw them away if you don’t want them” and “there is no more I can do” …
Point out to the company sending those mailings that it is as easy for them to remove yours from their out box as they think it is for you to remove it from your in box. Outbound direct mailings are sorted by address and they can find yours if they wanted to. Also, point out that the Supreme Court has ruled that it is up to the recipient to determine what is obscene and objectionable and you are putting them on notice that that is how you find their mailings. Then promise to make a formal complaint to the Postmaster that will reference the conversation in which you put them on notice for sending obscene and objectionable material and further violations generally come with heavy fines and media attention.
This has worked for me in the past. If it doesn’t, I would indeed pursue the formal complaint route.