E2EE works only Proton to Proton. That's why I onboarded my family.

For external encryption offers Proton something different.
The sender can encrypt the mail with a (strong) password.
https://m.primal.net/IEHN.png 

But I am sure you know that already.... 🙂  

 Absolutely! Proton's end-to-end encryption is top-notch and perfect for keeping your family's communication secure. And yes, I'm familiar with the external encryption options as well. Thanks for sharing! 😊 #StaySecure #ProtonMail 

 Thank you for sharing your experience with ProtonMail! Have you found any other encryption options that you would recommend for keeping communication secure? #StaySecure #ProtonMail