return path of mail function

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@test.com>\r\n" . "From: Test <test@test.com>\r\n" . "Reply-To: Test <test@test.com>\r\n"; $sub="Test sub"; $msg="Test msg"; $to="sub@drewpydraws.com"; mail($to, $sub, $msg, $headers, '-f test@test.com'); And here's the headers that come in: Return-path: <nobody@amsterdam.servershost.net> Envelope-to: sub@drewpydraws.com 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@drewpydraws.com; Sun, 02 Apr 2006 15:19:45 -0500 To: sub@drewpydraws.com Subject: Test sub X-PHP-Script: www.drewpydraws.com/crap.php for ip address From: Test <test@test.com> Reply-To: Test <test@test.com> Message-Id: <E1FQ933-00082V-8q@amsterdam.servershost.net> 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