I just went through the process of signing up to stop junk mail and thought folks might dig some deets.
Some of the steps are described here;
https://www.consumer.ftc.gov/articles/0262-stopping-unsolicited-mail-phone-calls-and-email
Phone calls
www.donotcall.gov
Credit Offers
https://www.optoutprescreen.com/
Magazines, catalogs, etc.
For most junk mail you can sign up to stop it via https://dmachoice.thedma.org/register.php - they charge you $2 to do it, or $3 if you do it by mail.