I'm not nearly as sure. The mechanics of one aren't that hard to imagine. Encourage spammers and make it cheap. Don't ever fight them at their source. Invoke mechanisms that intentionally destroy public utility in public protocols. Force everyone to rely on a small handful of "reputable" senders.
Working backwards from "who decides reputation anyways?" might make it easier to see.
Sending requires quite a large volume for the big players to allow you to play. The only viable option for small servers is to use a SMTP relay service. Amazon's was a pain to get out of the sandbox mode but has been reliable and most importantly free.
As I care more about the recieving side than sending emails this works well enough for me.
So, they have a "de facto" monopoly, or at best, are working with other providers to create a cartel.
> Email on a personal machine and domain has been dead for over 10 years.
Due to the actions of?
> You can receive it, no problem. But you can't send it.
You can send it. They're actively deciding to just block you. Then provide you no recourse.