[Evolution] Problem singing with pgp X509

["Trujillo Carmona, Antonio" <antonio trujillo sspa juntadeandalucia es>]

Sorry but I have evolution in Spain so I try to translate the option
from Spain to English, but it can be a few different
I live in Spain and work for our regional government (in a hospital).
We must use a X509 sing in our e-mail, I obtain it with no problem (with
firefox export it and import in evolution, throw preferment ->
certificate -> import, all that without problem, after that in  my
email's properties I select it in MIME section and in the last choice
(crypt's certificate, my be?), I don't know what put in the first line
(ID of GPG/PGP) so I copy and paste the same that in the sing cert (what
I chose in MIME section).
After that I try to sing a e-mail and I obtain the follow error:
****************************************************************
No se pudo crear un mensaje.

Debido a «gpg: omitido "TRUJILLO CARMONA ANTONIO": clave secreta no
disponible
gpg: signing failed: clave secreta no disponible
», quizá necesite seleccionar diferentes opciones de correo.
****************************************************************
I try to translate
****************************************************************
It couldn't create the message.

Due to «gpg: omit "TRUJILLO CARMONA ANTONIO": secret Key not available
gpg: signing failed: secret key not available
», my be you must select different options in mail.
-- 
trujo <antonio trujillo sspa juntadeandalucia es>