Examination of recipient's signing preferences yielded that the message should be signed using OpenPGP, at least for some recipients; however, you have not configured valid OpenPGP signing certificates for this identity.
O exame das preferencias de asinado dos destinatarios revelou que a mensaxe debería asinarse empregando OpenPGP, ao menos para algúns destinatarios; porén, non ten configurado ningún certificado de sinatura OpenPGP para esta identidade.