Version:           1.8.1 (using KDE 3.4.1 Level "a" , SUSE 9.3 UNSUPPORTED)
Compiler:          gcc version 3.3.5 20050117 (prerelease) (SUSE Linux)
OS:                Linux (i686) release 2.6.11.4-21.7-smp

Consider an e-mail with a from-header like this:

From: Name <namewithoutdomain>

(instead of "From: Name <name@domain>").
The message viewing windows then shows the following:

From: Name <>

(The email address is empty for all choices of Headers-Layout, except "All headers"). 

Even more annoying is this: 
After pressing "reply" the "To:" field of the message composer remains empty.

This is very annoying because the only way to find out the email address to reply to is by looking at the email source or by switching to "all headers".

There is a somewhat similar but different bug described at "http://bugs.kde.org/show_bug.cgi?id=90961"