[Exim] System Filter weirdness

Hello Experts,

I am trying to deliver mail using the system filter using this rule:

if first_delivery and $header_to: is "topdog@???"
 then
    unseen deliver underdog@???
endif

When I send an e-mail and check on underdog's delivery location I see
something weird - Envelope-to: system-filter


<cut>
>From pipind@??? Sat Nov 16 13:12:34 2002

Return-path: <pipind@???>
Envelope-to: system-filter
Delivery-date: Sat, 16 Nov 2002 13:12:34 +0300
Received: from [216.136.172.69] (helo=web11703.mail.yahoo.com)
        by ns2.wananchi.com (Exim 4.10.11 #2 (FreeBSD))
        protocol: smtp
        id 18CzwH-000KxF-00
        for <crown@???>
        ; Sat, 16 Nov 2002 13:12:33 +0300
Message-ID: <20021116101300.24875.qmail@???>
Received: from [62.8.64.15] by web11703.mail.yahoo.com via HTTP; Sat, 16 Nov 2002 02:13:00 PST
Date: Sat, 16 Nov 2002 02:13:00 -0800 (PST)
From: Washington Odhiambo <pipind@???>
Subject: Test Test
To: topdog@???

Have I mixed up something? I believe the Envelope-To: is supposed to
have underdog@???, no??



-Wash

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