problem with verp

Hello,

I'm using qmail with vpopmail on my system and just encountered the
following problem. I'm using qmail-inject with VERP per recipient to
the bounced emails of my mailing list called fpost (the domain is
freepoint.de).
The message-header looks like:

Return-Path: <fpost-tow.de-joneleit=tow.de@freepoint.de>
Delivered-To: joneleit@tow.de
Received: (qmail 7269 invoked by uid 0); 7 Jul 2003 12:52:52 -0000
Date: 7 Jul 2003 12:52:52 -0000
Message-ID: <20030707125252.7268.qmail@mx.freepoint.de>
Content-Type: text/html; charset=utf-8
Content-Disposition: inline
Content-Transfer-Encoding: 7bit
MIME-Version: 1.0
X-Mailer: MIME-tools 6.108 (Entity 6.107)
From: fPost Mailer <fpost@freepoint.de>
To: Marco Joneleit <joneleit@tow.de>

That seems to by OK for me. But when I try to send an E-Mail to a non
existing account the bounced email looks like that:

Return-Path: <>
Delivered-To: freepoint.de-fpost-@freepoint.de
Received: (qmail 7302 invoked for bounce); 7 Jul 2003 12:52:54 -0000
Date: 7 Jul 2003 12:52:54 -0000
From: MAILER-DAEMON@mx.freepoint.de
To: fpost-@freepoint.de
Subject: failure notice

And the standard failure notice of qmail...

The environmentvariables look like:

Sender:
Newsender:
Recipient: freepoint.de-fpost-@freepoint.de
Local: freepoint.de-fpost-
Ext: fpost-
Ext2:
Ext3:
Ext4:
RPLINE: Return-Path: <>
DTLINE: Delivered-To: freepoint.de-fpost-@freepoint.de

The Problem is, that I have no idea where I can get the recipient
address from. Maybe I do something wrong. Any hints?

greetings
Marco