It may be that mail delivers trash for the most part. I pull it out of my mailbox and toss it into my trash barrel. The trash men charge more to take it away than USPS does to “deliver” it to me. I don’t want it. Junk mail is a totally useless activity. Like junk e-mail, which I never even look at.
shred the junk mail and use it as mulch in the bed of the hedges or fill in low spots in the yard, once the grass gets cut (mulch-blade) over it, it disappears.