This is well outside of the practical capabilities of anyone but a nation state or large commercial entity. Even then, it's hard. It's more practical for a physical letter than for digital stuff. For a digital service, you'd have to go down to cabling infrastructure or take something like the SpaceX route and launch satellites. If you need something between a few nearby buildings, it's more practical to come up with a solution, but anything further out ... you're kind of stuck.
I don't believe the law has ever been revoked that requires anyone sending documents through a non-USPS service* to include the appropriate USPS postage cancelled with a pen along with their shipment
* excepting a point-to-point courier service for some reason
The USPS carved out a few exceptions, like delivering urgent mail. Gaming the system will get you raided by armed agents of the enforcement arm of the USPS.
I really detest this kind of attitude. Yes, the government is NOT restricting what you can say in an online space. But at the same time, there is no government platform I can speak from. They're not stopping me from saying what I want but they're also not giving me a platform.
Why are we giving corporate entities a pass on tyranny? It's not like restricting people's liberties is only something the government can do.
My onboard, state of the art, military grade AI suite is detecting infantile sarcasm, irritability unrelated to the current topic, and a tone unbecoming of a hacker news commenter.