You kid, but I imagine this will quickly be abused by bad actors to harass victims of online doxxing as ordering pizzas and (in more serious cases) swatting is.
You just don’t accept the letter, nothing to pay then
Aren't public institution obligated to accept letters from the public?
It'd be a fair campaign for everyone to return their stamps by sending them affixed to complaint cards to their local councilperson or postmaster.