[scarmig]

Indeed, Usenet doesn't require IP to work. See UUCP[0].

Some gray beard can probably speak more intelligently than me about this, but I think people would basically specify a series of hops. Each hop would store-and-forward the message to the next hop. Nowadays people talk about delay and disruption tolerant networks, which use similar techniques.

[0] https://en.wikipedia.org/wiki/UUCP

[hga]

If you wanted to do "retail" level transactions like sending an email, you needed to know the path, like systemA!systemB!destinationsystem!user

Usenet systems had established neighbors communicating with UUCP and used a flooding algorithm to get messages to the entire network of systems. All built on top of these point-to-point links, could be done over the Internet (NNTP) but it wasn't required. This was a big enough thing that specialized modems for UUCP were popular: https://en.wikipedia.org/wiki/Telebit