Part of the challenge is that the postal reorganization act restructured the postal service to run like a corporation, and so they need to make money. One of the big ways they make that money is by partnering with marketers to send us junk.
More on this here: www.vice.com/en/article/8...
This website is helpful for unsubscribing from a bunch of junk mail. Ironically, you have to pay to *not* get that mail, but the cost has been worth it in my experience.
www.dmachoice.org