[imp] S/MIME IMP doesn't verify sender email?

[vuser1 at test123.ru]

When user1 send email signed by certificate issued to user2, IMP says 
that email verification is OK, though there should be warning, I think.
----------
From:     *vuser2 at test123.ru *
To:     vuser1 at test123.ru
Subject:     certificate is not mine!
    This message has been digitally signed via S/MIME.
    The message has been verified. *Sender: vuser1 at test123.ru.*
The S/MIME certificate of Thawte Freemail Member: View/Save in your 
Address Book
Show this HTML in a new window?
-----------
I have certificate issued to vuser2 at test123.ru, imported it to vuser1 
and send the mail above. Mozilla Thunderbird says that message signature 
is valid, but email address listed in sender certificate is different 
from address that was used to send this message.

Is there an option to say IMP to check sender email?