Whoa. If anyone else s wondering like I was how the hell this works, it’s basically a ZIP file that appears as HTML: https://github.com/gildas-lormeau/Polyglot-HTML-ZIP-PNG

You can receive but can’t reply from those addresses in Proton because of the way encryption works. Don’t use Proton if you want to keep sending from any other email address.

Edit: frankly, I wouldn’t bother switching unless you plan on using a custom domain for all your email needs. I’m a firm believer in using your own domain, because that way you can switch providers without needing to change your email address — you always own it, because you own the domain.