You can now instruct Facebook to encrypt every email it sends to you so by using PGP (Pretty Good Privacy). All you have to do is import your public PGP key into your Facebook settings and you’re good to go.
Facebook uses the well-established PGP scheme to encrypt messages and tools like Mailvelope for Gmail users now make it a bit more straightforward to generate and manage keys in order to read and write encrypted emails. Facebook users may not be familiar with PGP or be able to handle the complexity of using PGP, so it’s unlikely that many regular users will actually sign up for it.
TechCrunch made a good point about Facebook and PGP
“The problem here, of course, is that most people have no idea how public/private key email encryption works and how to even get started with it. In the wake of Edward Snowden’s leaks, a number of organizations, including Google, promised to completely hide the complexities of end-to-end email encryption from regular users. Very few of these products have materialized so far, however — not for lack of trying, but because this is actually a very complex problem, both from a technical and user experience perspective.”
Facebook PGP is now available globally. If you want to see if it’s available for your account, head to your Facebook settings, look for the contact info section and you should see the option to add a PGP public key.