Sorry for not making it clear. I've used P=P (or actually the correct name is p≡p or pEp) before when FairEmail wasn't existent or in its very early days, and K

Sorry for not making it clear. I've used P=P (or actually the correct name is p≡p or pEp) before when FairEmail wasn't existent or in its very early days, and K-9 still did not have material design. I believe the material design got backported to K-9. This was during a time when K-9 didn't get stable releases, and was lacking on development. They also use opportunistic encryption, but I frankly just assume e-mail is insecure communication and live with that thought. I've mentioned the applications (pEp and FairEmail) various times here and elsewhere.