I'm not eager to add any PGP support in Archiveopteryx. That shouldn't be needed, but is, because PGP's signature checking is much stricter than e.g. DKIM's. DKIM thinks a duck is a duck, PGP cares deeply about the details. A quoted-printable duck is not the same as a plaintext duck, and two quoted-printable ducks may not be the same either. Archiveopteryx faithfully implements sixty email-related RFCs and mail stored in or processed by aox frequently cannot be verified by PGP.
However. I care about encryption and privacy, and PGP has the mindshare and is widely considered The Solution. The problem with The Solution is that over the years, it has remained steadily at 0.0% adoption. At the moment slightly below 0.005% of email users have PGP keys, and some fraction of those 0.005% actually use PGP. I infer from that number that PGP has defects that block its adoption almost completely. I have some ideas what those defects are, but that doesn't matter, because whatever they are, their result is to block adoption.
This has been the case for 20 years, and by now I consider PGP to be hopeless. PGP hinders encryption and hurts our privacy, it doesn't help. I don't want to write any code to support that. Perhaps only ten lines of code and a few tests are needed, but I just don't want to write even that.
(Am I doing something else? Yes, I am, actually. I'll write about what later.)
Update: After writing the above, I suddenly remembered this old dystopian novel. The scenes in the 31st floor offices remind me of PGP. Worthwhile ernest people working hard, doing the best work they can.