Email used to be simple.
It used to be easy to setup and run your own private email server. I used postfix. If you wanted to send an email to someone@somewhere .com your server would look up s omewhere.com 's mail server address from it's DNS record, connect to it's port 25, somewhere.com would say "Hello", you said I have a message for someone , and somewhere.com would say great - send it over. Now it's all encryption, domain authentication keys, permitted sender policies, spam checks, scam checks, etc, etc, etc. I gave up and went back to my native gmail address. Let the experts try and keep up.