Crypted & Signed from Outlook Express

Hello

today i discovered that e-mail send from Outlook Express (Vers. 6 /
XP-SP3) are not decrypted by Djigzo when they are additionally signed.
The same e-mail Signed & Crypted from Thunderbird works as expected.
The header are as follow :

Outlook
Content-Type: application/x-pkcs7-mime;
  smime-type=enveloped-data;
  boundary="----=_NextPart_000_0022_01CA6E9B.53470530";
  name="smime.p7m"
Content-Transfer-Encoding: base64
Content-Disposition: attachment;
  filename="smime.p7m"
X-Priority: 3
X-MSMail-Priority: Normal
X-Mailer: Microsoft Outlook Express 6.00.2900.5843
X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2900.5579

Thunderbird
Content-Type: application/x-pkcs7-mime; name="smime.p7m"
Content-Transfer-Encoding: base64
Content-Disposition: attachment; filename="smime.p7m"
Content-Description: S/MIME Encrypted Message

I guess its OE doing nasty things but the question is, if there is
something Djigzo can do to decrypt the message anyway.

Many Thanks

Andreas