Version: 1.6 (using KDE 3.2.0, Gentoo) Compiler: gcc version 3.2.3 20030422 (Gentoo Linux 1.4 3.2.3-r4, propolice) OS: Linux (ppc) release 2.4.24-ben1 Mime tree should not be shown if 1) "only non plaintext" is selected and 2) message contains only plaintext + pgp sign Sign is rarely viewed/saved, and if you really want to see it you can add a link to it in the red/yellow/green (crypto?) bar. BTW the "structure viewer" is not shown (and there is no direct way to view the sign) if the message is signed but not incapsulated in multipart.
If the message is clearsigned then the message is a simply plain/text message. There's no point in showing the message structure in this case because it consists of exactly one item. Whether the message structure should be shown for signed messages with detached signatures pretty much a matter of taste. Instead we should have a two modes for the messages structure viewer: The current one and a simple mode where only real attachments are listed.
In KMail of KDE 4.4, the message structure viewer is not shown automatically at all, even for non-plaintext messages.