JMAP is for talking to the server. You don't want the server to have access to the plain text, only encrypted blobs, so that's the only thing that JMAP should g

JMAP is for talking to the server. You don't want the server to have access to the plain text, only encrypted blobs, so that's the only thing that JMAP should give you. If JMAP dealt with providing the plain text, that means the server would be able to decrypt and that defeats the whole point of End-to-End Encryption. Fortunately, Fastmail has a blog post that goes more in depth on the subject: https://fastmail.blog/2016/12/10/why-we-dont-offer-pgp/ https://fastmail.blog/2016/12/10/why-we-dont-offer-pgp/ What you want is something on top of emails, like autocrypt (https://autocrypt.org/ https://autocrypt.org/)