Nothing stays private these days. The word privacy doesn't seem to exist any more. If the government, Big Brother or whoever wants to take a look at your emails, they will, and nothing can prevent them from doing so. Sad, but true.
Essentially, one is looking for a country which respects the rule of law, human rights, is properly democratic, and is not able to be strong-armed by the US, Russia or China. Sadly, there don't appear to be any answers to this one. That probably compels us to look for services which can be securely split across multiple uncooperative jurisdictions.
Back to my soapbox. There are about 10 folks on here with whom I know for sure I can communicate privately, because we all share the same passion for making it happen. So yes in fact its easy to do for ME and those like me. But your day to day "friends" will never participate and for those folks its all out in the open. Just how it is.
Well, with onion service email providers, finding the actual mailserver is nontrivial. Adversaries can hammer clearnet gateways all they like, but that's just a temporary DDoS headache. And then there are the various onion service messaging sites, Pond, Bitmessage, pastebins, etc, etc. And of course, you use end-to-end encryption
Agree, the services with true client code with PFS and onion providers are harder to attack. But for services the class of Protonmail etc, if you can't trust the jurisdiction that much, you're vulnerable to having nasty modified javascript encryption code being downloaded to the browser.
I am not sure its possible to communicate in a "totally private" way using clearnet - ever. As long as you are willing to portray a psuedo-personality you could communicate in an "eyes only" way using email body encryption. It would be linked to your psuedo and not you, but that is a far cry from leaving clearnet where the entire communication trunk is "gone".