Physical mail costs money, but 80% of the mail I receive is junk mail that somebody has paid to send me.

Of the 20% of mail that is useful to me, it's still pretty much all just from corporations who have decided to send me a physical letter even though they have my e-mail - e.g. the water company sends me some brochure to somehow justify how much money they're charging by breaking down what they spend all their money on etc...

I get almost zero "real" mail from actual people nowadays. Now it costs £1.80 to post something first class and 91p second class, real mail is basically limited to birthday and Christmas cards. I myself send so few letters, than I still have a couple of stamps in my wallet that I technically bought 6 years ago when they cost 35% the current price (although they were replaced with barcode versions by sending them in to Royal Mail).

Plenty of companies pay the post office to deliver paper spam to my mailbox each day. I don't want any of that, either. "Free" makes spam easier, but a cost doesn't prevent it.

that is what I was thinking