Version:            (using KDE KDE 3.5.2)
Installed from:    Ubuntu Packages
OS:                Linux

I enabled the "use quoted-printable" option on the smtp-server list page. If I send a normal E-Mail, without signing it, everything works right. The message is correctly encoded using quoted-printable. (I use utf-8 as the default charset) 

If I sign the message (using PGP-Inline) KMail gets it wrong. The interesting headers change to this:

Content-Type: text/plain;
  charset="utf-8"
Content-Transfer-Encoding: 7bit
Content-Disposition: inline

Although I use special letters like ä, ü, ö or €, in the text part of the message these characters are not encoded using quoted-printable but in 8-Bit format.

Because of that, users of other E-Mail clients cannot read my messages properly.