I'd pay a fee for mail service if I must. Worth it. Just end unsolicited bulk mail, and make solicited bulk mailers ask me to opt in again every year or so, and stop on a negative response, or none at all. It's not free speech, it's my friggin' mailbox, and others shouldn't be able to damn near DOS it just because they want me to know about their special offer or lie to me about politics. I get that the postal service needs that money to stay afloat, hence my being cool with a fee of some sort replacing the bulk mailing.
For that matter, I'm not sure how a good portion of junk mail isn't fraud or false advertising or something along those lines. I get a lot of really deceptive commercial mail, pretending to be things that it isn't, like official notices, bills, credit cards (god those fake card advertisements are stupid), and so on.