Sterna now sends and reads encrypted email with OpenPGP. Install the companion OpenKeychain app, choose your key in an account's settings, and a padlock button in the composer lets you sign your mail (proving it came from you) and encrypt it (so only your recipient can read it), on both JMAP and IMAP accounts. Incoming encrypted mail is decrypted as you open it, with a coloured badge showing whether the signature checks out. Decrypted content is never written to disk; an attachment you open is written to the app's own storage until the cache is cleared. The subject line is not encrypted. A short guide is in ENCRYPTION.md.
