Version:           1.7 (using KDE KDE 3.3.1)
Installed from:    Debian testing/unstable Packages

When re-editing an unsent but signed message and changing the transport (identity) to one without gpg-key, the signature is removed but message structure remains.
I did:

- wrote a message with Identity_A, signed it and tried to sent
- because sending didn't work, re-edited message, changed Identity to Identity_B (that does not have a gpg-key)
- pushed send-button

This is how the headers look after this, message is not displayed (only if you view the source, but then special characters are mixed up):

From: 
X-KMail-Transport: Identity_B
To: 
Subject: test
Date: Mon, 8 Nov 2004 22:36:44 +0100
User-Agent: KMail/1.7
MIME-Version: 1.0
Message-Id: <200411082236.44416. >
Status: R
X-Status: NQC
Organization: 
X-KMail-Identity: 25326826
Content-Type: multipart/signed;
  boundary="nextPart1581337.zJM63TceXe";
  protocol="application/pgp-signature";
  micalg=pgp-sha1;
  charset="us-ascii"
Content-Transfer-Encoding: 7bit
Content-Disposition: inline
X-KMail-EncryptionState: N
X-KMail-SignatureState: N
X-KMail-MDN-Sent:  

test