I honestly don't like the email analogy. I mean, there are no email servers that are defederated or something. "Why don't you answer my mails?" "Oh, you have a gmail adress? That's banned on my instance, sorry, not my fault."

But until I find a better one, I will continue using it.

Edit: Since I got some replies explaining that defederation in email servers is a thing, thanks, I wasn't aware of that. Still, my point holds that that's not a basic feature associated with mails. I don't think about which server to choose based on which servers are defederated. So explaining the fediverse to an uninitiated and relying on a feature that's huge in the fediverse but not even I'm aware of it in the context of mails, isn't good.

Tldr, I just moved to goalpost from "this doesn't exist" to "this isn't something normies are aware of"