Well, if we're going to be pedantic, then you should make room for the Telegraph network which served a similar function between the postal and telephone networks (and later the internet) as documented in Tom Sandage's _The Victorian Internet_.[1]
Yeah, no. I have thought about this but the problem is that the lay person cannot use a Telegraph. Yes, of course they can go to an office and send a telegraph message, but that's different because now that's clearly mediated and what I came up with is that the crucial thing is the lack of mediation.
If the UPU begins a thousand years earlier that falls by the same reasoning, a thousand years earlier too many people aren't literate, so they need to have their letter written by someone else, and the recipient must find someone to read it - but by the time of the UPU literacy is widespread.
[1] https://en.wikipedia.org/wiki/The_Victorian_Internet
If the UPU begins a thousand years earlier that falls by the same reasoning, a thousand years earlier too many people aren't literate, so they need to have their letter written by someone else, and the recipient must find someone to read it - but by the time of the UPU literacy is widespread.