Hi again,

regarding my problems with Gnus + SMIME + GnuPG, there is another thing
that I don't seem to be able to solve:

It is very weird, maybe a bug, because I have set epg-pinentry-mode to
loopback, which is supposed to use the Emacs minibuffer to ask for the
passphrase of private keys. This works perfect for PGP but it throws an
error for SMIME "Signing failed (unknown reason)". [If I set
epg-pinentry-mode to 'nil, then I am asked for the passphrase by
gnome-keyring and all is good (but I need to use the mini-buffer, since
I use this machine mostly remotely].

I chased the error down to the function "epg-sign-string" in epg.el, but
my ELisp is very rusty and not making much progress in debugging the
issue. I guess at some point epg.el is calling pinentry, but don't know
how to efficiently debug this.

Any pointers/advice much appreciated.

Cheers,
-- 
Ángel de Vicente                 -- (GPG: 0x64D9FDAE7CD5E939)
 Research Software Engineer (Supercomputing and BigData)
 Instituto de Astrofísica de Canarias (https://www.iac.es/en)