certificate x.509 and outlook express 6

[fabio miotti <fabiotest80 () libero it>]

In some cases Outlook Express shows a wrong certificate when i receive a 
signed and encrypted message from another user.
Outlook Express uses the sender's certificate to encrypt the message, and 
not the receipt's certificate!
Notwithstanding this, outlook express open the message, but this means the 
sender's private key is seen by the receipt.