>just because they can and will do anything to maintain their monopoly.

This is a popular opinion on HN but it doesn't seem at all inline with reality. Email isn't exactly a real money maker for anyone. And the amount of email spam and abuse is immense. Filtering out most unknown providers is unfortunately extremely effective. Almost all spam wiped out with a simple check.

Maybe the ideal solution would be to let you link your custom email domain with a google account so you can have your google account vouch for the legitimacy of your custom domain. But even then, some of the time your email server actually is just blasting out spam without you knowing it.