You can also run your own mail servers, even non-technical people could do that with for example https://thehelm.com/. Haven't tried it out myself, though.
Which solves nothing if the other party's email is provided by Google. Google is still getting your chats.
Re:COI – Chat Over IMAP
by richardwhiuk on Thursday February 21, 2019 @10:53AM
(#19217656)
XMPP and Matrix other people can host their servers on Google as well.
Fundamentally, if you don't trust the decisions of the person you are talking with, you can't guarantee the privacy of your chats.
Re:COI – Chat Over IMAP
by elvecinodeabajo on Thursday February 21, 2019 @09:10PM
(#19222523)
You're forgetting E2E encryption.
"With XMPP and Matrix.org -based services you would still need to convince everyone to join your new network. Easy in theory, very complex in practice!"
I don't find that so problematic. People just needs to see a bit the inner workings to feel a bit comfortable and give it a chance.