Notes

If you’re hoping Protonmail exposes the PGP public keys of their users on some keyserver, you’re wrong. So, unless the recipient attached its public key, or has it published somewhere, tough luck.

But you can request it from their API service:

$ curl -s 'https://api.protonmail.ch/pks/lookup?op=get&search=barrack.ossama.binladen@protonmail.com'

Or open https://api.protonmail.ch/pks/lookup?op=get&search=barrack.ossama.binladen@protonmail.com in your favorite browser. Remember to replace the email address with the actual address of the person you want his or hers PGP public key. The funny thing is there is someone with that email address (barrack.ossama.binladen@protonmail.com). Heh.

Thanks a lot, Protonmail.