I genuinely don’t understand this parallel, but I would like to. It feels like I’m missing something. Email has to go to a specified recipient every time. A post is avail to everyone in the community + federated instances.
The parallel is that email is built on a standard (well, two; RFC-5321 and RFC-5322), and it doesn’t matter what email server you use, whether it’s Gmail or Hotmail or a box in your basement running postfix, they’re all supposed to follow the standard and talk to each other; that is, they form a federated network. In the fediverse, we mostly use the ActivityPub standard, but the idea is the same.
XMPP is probably a technically better comparison, but try making that comparison to your parents. The point of the email comparison, even if it’s slightly less technically accurate, is that people have actually heard of email
