PGP/MIME Encryption
In K-9 we aim to support OpenPGP, a specification of Pretty Good Privacy (PGP), an encryption method developed in the early 90s that uses a 'web of trust' to validate certificates.
In previous releases of K-9 Mail we have supported basic integration with Android Privacy Guard (APG).
However with development on the project stalled and with a desire to better support PGP/MIME in the app, newer releases (5.200 and later) move to support OpenKeychain via a public API which we hope other apps which want to provide PGP key storage can support.