If you want to send something securely, I’m not sure email is the best method. Even if you understand all the risks and pitfalls and side-step the minefields it’s still insecure in non-fixable ways. ProtonMail make a service out if it mitigating those issues as best they can (but even they explain their threat-model and what they DON’T mitigate. Others such as Silent Circle ended up giving up.
You could recommend to those non-technical people to either:
- Use Signal
- Sign up to two free ProtonMail accounts and use those to exchange with one another. That way they’re both e2e and don’t leave the eco-system. And no setting up of PGP keys and such like, and a nice web UI.
If they’re non-technical I wouldn’t suggest PGP IMHO. It’s actually easier to setup S/MIME for non-technical people (I’ve had some success there myself).
Of course part of this is that no one has solved the UX and usability and that it never reached mainstream in most ‘typical’ email clients. To set it all up you have to be fairly technical. When it should just work out of the box - like Signal.