Email is inherently insecure and not private. If you need private and secure communication use a different protocol.
If you just don’t want Google or Microsoft to read through your emails ( completely reasonable) then that’s where the “private” and “encrypted” providers come in, imo.
No matter what, your email provider can read all of your emails if they want unless you encrypt the actual content before sending. But even then the meta data is all available. So you have to trust your email provider.
But also it’s not a secure protocol. Pick something better if you need security and privacy.