Except from RFC 821 SIMPLE MAIL TRANSFER PROTOCOL http://www.ietf.org/rfc/rfc0821.txt, pp. 21/22:
When the receiver-SMTP makes the "final delivery" of a message it inserts at the beginning of the mail data a return path line. The return path line preserves the information in the <reverse-path> from the MAIL command. Here, final delivery means the message leaves the SMTP world. Normally, this would mean it has been delivered to the destination user, but in some cases it may be further processed and transmitted by another mail system.
It is possible for the mailbox in the return path be different from the actual sender's mailbox, for example, if error responses are to be delivered a special error handling mailbox rather than the message senders.
The preceding two paragraphs imply that the final mail data will begin with a return path line, followed by one or more time stamp lines. These lines will be followed by the mail data header and body [2].
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Here's a sample IMail header, and there's absolutely no trace of
Envelope-Sender in the header. The absent Return-Path header is causing problems for a system I am designing, and I know of no other reasonable
MTA (i.e. sendmail, postfix, qmail, exim, Courier, mh, etc) that has failed to record the envelope sender address in the last five years.
Delivered-To: [EMAIL PROTECTED]
Received: from mail.cfpros.com (65.218.70.100) by squish with POP3 for
<[EMAIL PROTECTED]>; 26 Feb 2004 23:38:12 -0000
Received: from roam.unifiedmind.com [209.164.72.58] by wwip1
(SMTPD32-8.04) id A31185022E; Thu, 26 Feb 2004 17:36:49 -0600
Received: (qmail 21744 invoked from network); 26 Feb 2004 23:45:57 -0000
Received: from unknown (HELO jamesthornton.com) ([EMAIL PROTECTED])
by 0 with SMTP; 26 Feb 2004 23:45:57 -0000
Message-ID: <[EMAIL PROTECTED]>
Date: Thu, 26 Feb 2004 17:35:33 -0600
From: James Thornton <[EMAIL PROTECTED]>
User-Agent: Mozilla/5.0 (Windows; U; Windows NT 5.0; en-US; rv:1.4) Gecko/20030624 Netscape/7.1 (ax)
X-Accept-Language: en-us, en
MIME-Version: 1.0
To: [EMAIL PROTECTED]
Subject: test return path
Content-Type: text/plain; charset=us-ascii; format=flowed
Content-Transfer-Encoding: 7bit
X-RCPT-TO: <[EMAIL PROTECTED]>
Status: R
X-UIDL: 377596421
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James Thornton _____________________________________________ Internet Consultant, http://jamesthornton.com
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