Version:           1.5.3 (using KDE 3.1.3)
Installed from:    SuSE
Compiler:          gcc version 2.95.3 20010315 (SuSE)
OS:          Linux (i686) release 2.4.18-4GB

I sometimes receive mails in with headers like this:

==
Content-Type: text/plain
Message-Id: <1062088113.3307.76.camel@tfoottit2>
Mime-Version: 1.0
X-Mailer: Ximian Evolution 1.4.0 
Date: 28 Aug 2003 12:28:33 -0400
Content-Transfer-Encoding: 7bit
cc: kevin mulholland <Kevin.MULHOLLAND@REMOVEDFORPRIVACY.com>
cc: Opie Mail List <opie@handhelds.org>
X-BeenThere: opie@handhelds.org
X-Mailman-Version: 2.1
Precedence: list
Reply-To: tfoottit@REMOVEDFORPRIVACY.com
==

As you can see, there are _two_ cc header fields. KMail only recognizes the first. This causes problems for filtering (filters on CC aren't triggered) and confusion when looking at the message as you have no idea how it ended up in your mailbox (so you assume a BCC...) I think KMail should concanate all addresses found in cc headers into one cc field, so it shows up when viewing the message and filters work on this field.