return path of mail function

["Andrew Darrow" <vrspectre@xxxxxxxxx>]

I'm having a problem setting the return-path using the mail function. I seem to be able to modify any of the other header information I want, but not this one item. 

Here's my code:
$headers =  "Return-Path: Test <test@xxxxxxxx>\r\n" .
   "From: Test <test@xxxxxxxx>\r\n" .
   "Reply-To: Test <test@xxxxxxxx>\r\n";

$sub="Test sub";
$msg="Test msg";

$to="sub@xxxxxxxxxxxxxxx";

mail($to, $sub, $msg, $headers, '-f test@xxxxxxxx');




And here's the headers that come in: 
Return-path: <nobody@xxxxxxxxxxxxxxxxxxxxxxxxx>
Envelope-to: sub@xxxxxxxxxxxxxxx
Delivery-date: Sun, 02 Apr 2006 15:19:45 -0500
Received: from nobody by amsterdam.servershost.net with local (Exim 4.52)
 id 1FQ933-00082V-8q
 for sub@xxxxxxxxxxxxxxx; Sun, 02 Apr 2006 15:19:45 -0500
To: sub@xxxxxxxxxxxxxxx
Subject: Test sub
X-PHP-Script: www.drewpydraws.com/crap.php for ip address
From: Test <test@xxxxxxxx>
Reply-To: Test <test@xxxxxxxx>
Message-Id: <E1FQ933-00082V-8q@xxxxxxxxxxxxxxxxxxxxxxxxx>
Date: Sun, 02 Apr 2006 15:19:45 -0500
X-Antivirus: AVG for E-mail 7.1.385 [268.3.4/299]
Mime-Version: 1.0
Content-Type: text/plain

The "From" and "Reply-To" get set correctly so it works fine on e-mail clients, but some of the messages will be delievered to cell phones that display the return-path instead of from and reply-to. 

Any thoughts on how I would go about setting the value for Return-Path?

~Drew
www.drewpydraws.com