aarcane@web:/media/www/website/pages$ sudo -u www-data sendmail aarcane@aarcane.org
To: aarcane@aarcane.org
From: aarcane@aarcane.org
Return-Path: aarcane@aarcane.org
Reply-To: aarcane@aarcane.org
Sender-Address: aarcane@aarcane.org
Subject: This is a test.  return-path info should show aarcane but it probably shows www-data.
.
aarcane@web:/media/www/website/pages$


The web server runs as www-data, so all mail sent from a website gets sent as system user www-data.

Delivered-To: aarcane@gmail.com
Received: by 10.142.242.2 with SMTP id p2cs75299wfh;
        Sat, 22 Dec 2007 11:56:14 -0800 (PST)
Received: by 10.100.128.20 with SMTP id a20mr3854709and.35.1198353373617;
        Sat, 22 Dec 2007 11:56:13 -0800 (PST)
Received-SPF: fail (google.com: domain of www-data@aarcane.org does not designate <unknown> as permitted sender)
Received: by 10.54.1.76 with POP3 id 76mf168486wra.4;
        Sat, 22 Dec 2007 11:56:13 -0800 (PST)
X-Gmail-Fetch-Info: aarcane@aarcane.org 2 aarcane.org 110 aarcane
Return-Path: <www-data@aarcane.org>
X-Original-To: aarcane@aarcane.org
Delivered-To: aarcane@aarcane.org
Received: from web.aarcane.org (web.aarcane.org [10.66.6.11])
	by aarcane.org (Postfix) with ESMTP id BEFDEC3A2
	for <aarcane@aarcane.org>; Sat, 22 Dec 2007 19:53:50 +0000 (UTC)
Received: by web.aarcane.org (Postfix, from userid 33)
	id 7078A141B67D; Sat, 22 Dec 2007 19:53:50 +0000 (UTC)
To: aarcane@aarcane.org
From: aarcane@aarcane.org
Reply-To: aarcane@aarcane.org
Sender-Address: aarcane@aarcane.org
Subject: This is a test.  return-path info should show aarcane but it probably shows www-data.
Message-Id: <20071222195350.7078A141B67D@web.aarcane.org>
Date: Sat, 22 Dec 2007 19:51:27 +0000 (UTC)

This is what it looks like on the other end.  Note the header: Recieved-SPF: fail and the header Return-Path: <www-data@aarcane.org>