Version:           4.8 (using KDE 4.8.0) 
OS:                Linux

When I created filter with *cat* program in pipe, and use this filter on some messages, KMail modify headers. In result, html mail is no longer displayed correctly.

I expect that new (filtered) message should be same as original, when I use *cat* program. Or I misunderstand what pipe filter mean?

This behavior breaks any spam filter!

Reproducible: Didn't try

Steps to Reproduce:
I have one simple filter with cat program in pipe

[Filter #0]
Applicability=0
AutomaticName=true
ConfigureShortcut=false
ConfigureToolbar=false
Enabled=true
StopProcessingHere=false
ToolbarName=Bogofilter Check
action-args-0=cat
action-name-0=filter app
actions=1
apply-on=check-mail,manual-filtering
contentsA=256000
fieldA=<size>
funcA=less-or-equal
identifier=HOK0Iz22cIN8toEj
name=Bogofilter Check
operator=and
rules=1

[General]
filters=1


Original HTML message recieved with KMail:


Received: from ironport5.centrum.cz (unknown [10.32.3.101])
	by gmmr5.centrum.cz (Postfix) with ESMTP id B041080175A7
	for <lukas.karas@centrum.cz>; Sat,  4 Feb 2012 18:05:48 +0100 (CET)
X-IronPort-Anti-Spam-Filtered: true
X-IronPort-Anti-Spam-Result: Al4BADNkLU/RVdeykGdsb2JhbABDgl2CLoR+pDdiCCIBAQEBCQkNBxQEHQSCCwIFCh0BGx4DEggBAi4OAiURAQUBIjWHXZkAgl0KiyZLgnCEOz+IcQIFC4wEBgEqEwIDAQEBAQEBAQGCeQUCAgQBCwICBAUDAwMBBQUBZwEEBCQEghmBFgScOYcLPYQD
Received: from mail-ey0-f178.google.com ([209.85.215.178])
  by mx.centrum.cz with ESMTP; 04 Feb 2012 18:05:48 +0100
Received: by mail-ey0-f178.google.com with SMTP id o10so1997149eaa.23
        for <lukas.karas@centrum.cz>; Sat, 04 Feb 2012 09:05:48 -0800 (PST)
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed;
        d=gmail.com; s=gamma;
        h=message-id:date:from:to:subject:x-mailer:mime-version:content-type;
        bh=K4MBVe6UZavBlrfxwwwwa4FkOBE+od9SOSQD5xtAF1A=;
        b=SD9j39RxBLyI5ZbcwI3y4esmeYXNIsn+IFOf7JFFI/d46Y/o73DAIl9EVP8QyzjA0y
         KUggVfCmBjhcgQ/6wASJfdrcdI8PI+GyjrS2cKi9yg+qGdp5vpb/rCiTrx+u6Z/UKFg8
         v+bWXQxuycEa/Hh+H/CpHU3G7xrI8OwRRSvgs=
Received: by 10.213.9.4 with SMTP id j4mr1872698ebj.100.1328375148460;
        Sat, 04 Feb 2012 09:05:48 -0800 (PST)
Received: from www.palm.com (ip-85-161-86-7.eurotel.cz. [85.161.86.7])
        by mx.google.com with ESMTPS id t11sm37047468eea.10.2012.02.04.09.05.46
        (version=SSLv3 cipher=OTHER);
        Sat, 04 Feb 2012 09:05:47 -0800 (PST)
Message-ID: <4f2d656b.0b230e0a.39c4.fffff3ff@mx.google.com>
Date: Sat, 04 Feb 2012 18:05:47 +0100
From: <karry.cz@gmail.com>
To: "=?UTF-8?Q?Luk=C3=A1=C5=A1_Karas?=" <lukas.karas@centrum.cz>
Subject: Test
X-Mailer: Palm webOS
MIME-Version: 1.0
Content-Type: multipart/mixed; boundary="Multipart_=_Boundary_=_1328375146"


--Multipart_=_Boundary_=_1328375146
Content-Type: text/html; charset="UTF-8"
Content-Transfer-Encoding: quoted-printable

Mail content
--Multipart_=_Boundary_=_1328375146--


After process filter (Ctrl+J), message source is:

Received: from ironport5.centrum.cz (unknown [10.32.3.101]) by gmmr5.centrum.cz (Postfix) with ESMTP id B041080175A7 for <lukas.karas@centrum.cz>; Sat,  4 Feb 2012 18:05:48 +0100 (CET)
X-IronPort-Anti-Spam-Filtered: true
X-IronPort-Anti-Spam-Result: Al4BADNkLU/RVdeykGdsb2JhbABDgl2CLoR+pDdiCCIBAQEBCQkNBxQEHQSCCwIFCh0BGx4DEggBAi4OAiURAQUBIjWHXZkAgl0KiyZLgnCEOz+IcQIFC4wEBgEqEwIDAQEBAQEBAQGCeQUCAgQBCwICBAUDAwMBBQUBZwEEBCQEghmBFgScOYcLPYQD
Received: from mail-ey0-f178.google.com ([209.85.215.178]) by mx.centrum.cz with ESMTP; 04 Feb 2012 18:05:48 +0100
Received: by mail-ey0-f178.google.com with SMTP id o10so1997149eaa.23 for <lukas.karas@centrum.cz>; Sat, 04 Feb 2012 09:05:48 -0800 (PST)
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=gamma; h=message-id:date:from:to:subject:x-mailer:mime-version:content-type; bh=K4MBVe6UZavBlrfxwwwwa4FkOBE+od9SOSQD5xtAF1A=; b=SD9j39RxBLyI5ZbcwI3y4esmeYXNIsn+IFOf7JFFI/d46Y/o73DAIl9EVP8QyzjA0y KUggVfCmBjhcgQ/6wASJfdrcdI8PI+GyjrS2cKi9yg+qGdp5vpb/rCiTrx+u6Z/UKFg8 v+bWXQxuycEa/Hh+H/CpHU3G7xrI8OwRRSvgs=
Received: by 10.213.9.4 with SMTP id j4mr1872698ebj.100.1328375148460; Sat, 04 Feb 2012 09:05:48 -0800 (PST)
Received: from www.palm.com (ip-85-161-86-7.eurotel.cz. [85.161.86.7]) by mx.google.com with ESMTPS id t11sm37047468eea.10.2012.02.04.09.05.46 (version=SSLv3 cipher=OTHER); Sat, 04 Feb 2012 09:05:47 -0800 (PST)
Message-ID: <4f2d656b.0b230e0a.39c4.fffff3ff@mx.google.com>
Date: Sat, 04 Feb 2012 18:05:47 +0100
From: karry.cz@gmail.com
To: =?utf-8?B?THVrw6HFoQ==?= Karas <lukas.karas@centrum.cz>
Subject: Test
X-Mailer: Palm webOS
MIME-Version: 1.0
Content-Type: text/plain; charset="US-ASCII"


--Multipart_=_Boundary_=_1328375146
Content-Type: text/html; charset="UTF-8"
Content-Transfer-Encoding: quoted-printable

Mail content
--Multipart_=_Boundary_=_1328375146--




Expected Results:  
I expected that this filter don't change message.