It's not that dangerous. They'll talk to you about what your intent was. On the other hand it could be the companies mailing you junk with no reply for decades have the ill intent because they're trying to get people into committing felonies (entrapment) with dogshit offers nobody would ever take that are littering the mail system. So if they accuse you, tell them that accusation must be redirected--like mail is--to like a middle-manager in the company doing mass-mailings.
They didn't pay you anything to wade through their junk. You aren't their slave unless you sign.
And I don't open the mail -- that's a crime the postal service would take very seriously indeed. Sure, perhaps my practice is technically illegal, but I don't think it's the sort of illegal that the USPS would spend a lot of time and money on.
I'm not opening someone else's mail, I'm not preventing it from being delivered to the address on it, and I'm not preventing the recipient from receiving it. His death does that.
