kmail: strange behaviour with some s/mime encrypted emails

[Andreas Petzold]

Hi,

in kmail I routinely sign my emails using s/mime. I rarely use s/mime
encryption, but I haven't seen a problem for a long time. However,
recently a friend of mine sent me two encrypted emails. The first one
from kmail. No problems at all with that email.

The second one he sent from thunderbird and this email is shown as
garbled junk in the message preview pane as you can see here:

http://tinyurl.com/2jq4z6n

Only when I accidentally hit the Enter key the message was decrypted
and readable see

http://tinyurl.com/38fx3e

I asked a number of people to send me s/mime encrypted emails from thunderbird
and the result is always the same.

I had a closer look at the emails to try to find a difference. I found
a couple of small differences, but since I don't know (yet) what a
standard compliant s/mime encrypted email should look like, I don't
know which one is the reason of the problem:

* Attachments:
       - from thunderbird: kmail shows an attachment named "opaque signed data"
       - from kmail: kmail shows no attachment

* Header info:
       - from 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

       - from kmail:

Content-Type: application/pkcs7-mime;
      smime-type=enveloped-data;
      name="smime.p7m"
Content-Transfer-Encoding: base64
Content-Disposition: attachment; filename="smime.p7m"

Can one of the experts make sense of this?

Cheers,

Andreas