Yeah, the email example is an unintentional counterexample: it’s nearly impossible to run your own email server these days and not have your email rejected by everyone because the IP address is unrecognized and the spam filter is beyond reject-happy. To put it into fediverse terms: it’d be like federating with them, but where their CloudFlare DDOS protection blocks ActivityPub requests (this is actually what broke kbin’s federation a week or two ago so it’s not just a hypothetical!).

I go back and forth between reading it as “shit just works” and “shhhh, it just works”