I recognize that that is part of the protocol's design, but how common is that in practice on the modern Internet? If I'm using say, Outlook, or even some personal home server, and I have mail for example @ gmail.com, I would expect two things:

1. Microsoft, or my server, would look up the MX for gmail and send the email directly there, where I'd presume it's safe from maliciousness (obviously Google itself has access to it, I admit)

2. The only server that would accept mail from my server and relay it for me would be someone I'm paying, and they probably would accept it over TLS right?