Thanks for doing that checking.

On 1/4/20 4:37 AM, Mattias Engdegård wrote:

> the code in mml-smime.el looks like it fails to return failure from an unsuccessful encryption attempt

smime-encrypt-buffer always returns nil (it signals an error on failure), so
that code happens to work though it is too complicated.

I fixed that issue along with the others (other than the two that you and
Michael already fixed) by installing the attached into the emacs-27 branch.