Alexander Adolf writes: > Dear Notmuch Developers, > > I have trouble getting going with S/MIME. > > Emacs version: GNU Emacs 27.1 (build 1, x86_64-apple-darwin18.7.0, NS > appkit-1671.60 Version 10.14.6 (Build 18G95)) of 2020-08-12 > > notmuch version: notmuch 0.31+2~gd127b16 > (brew install notmuch --head) I'm a bit at a loss how to investigate this, not using SMIME or macOS myself. Could you try duplicating the problem with the notmuch test key / certificate? I've attached the test key and the ca from from the notmuch source. If you have the same behaviour with this key, then please share a message encrypted to this key that manifests the problem for you (probably as an attachement)