Sorry to awaken an old story from 2019, but I would love to know what frobs to tweak, to be able to decode PKCS7 S/MIME encoded payload.
MH-E is (I think) breaking out of the classic NMH path to do this, with the payload. So, I don't "see" a clean path in mhnshow definitions to do this. The fine mail archive terminates in 2019 with a discussion on how to SEND SMIME pkcs7. I just want to read at this point. I successfully imported my "own" work certificate via P12 -> Firefox -> P12 (in another format) -> gpgsm --import (gpgsm is fussy about what P12 "is" apparently)) so I have a .kbx now with this magic. And some call out from emacs is finding it. (getting MH-E working was this works bundle-of-joy. It actually went smoother than I feared, and that includes getting "modern auth" working with Outlook 365 backed inbound Mail via mbsync, but sending is classic password AUTH LOGIN over SMTP/587 via msmtp) all cluestick hits greatfully received. -G
