The attached patch "works for me", though it is not 100% logically correct.
It assumes that email containing the pkcs7-mime header and NOT having subtype smime-type, is encrypted, regardless of its Content-Description. Regards -Klaus
--- mutt-1.5.21/crypt.c.orig 2012-09-04 10:01:33.000000000 +0200 +++ mutt-1.5.21/crypt.c 2012-09-04 10:06:16.000000000 +0200 @@ -389,10 +389,17 @@ } /* Netscape 4.7 uses * Content-Description: S/MIME Encrypted Message - * instead of Content-Type parameter + * instead of Content-Type parameter. + * Unfortunately, this message is localized, so we + * can't really strcmp for it. + * Let's just assume for now, that the message is encrypted when + * subtype *pkcs7-mime is set, but the smime-type parameter + * is absent. */ +#if 0 if (!ascii_strcasecmp (m->description, "S/MIME Encrypted Message")) - return SMIMEENCRYPT; +#endif + return SMIMEENCRYPT; complain = 1; } else if (ascii_strcasecmp (m->subtype, "octet-stream"))