Have you checked out Catalog Choice? They have something similar called MailStop... https://www.catalogchoice.org/mailstop
You put a red dot (i.e. a red sticker, any sticker) in your mailbox, and they will NOT put junk mail in.
What's even sadder is I cannot fathom how you guys have this option. The US has literally grown up with junk mail - it's always about 99% of mail and we cannot fathom what life is like on the other side!
http://www.nytimes.com/2011/12/04/sunday-review/the-junking-...