From owner-freebsd-questions@FreeBSD.ORG  Thu Mar 23 15:40:27 2006
Return-Path: <owner-freebsd-questions@FreeBSD.ORG>
X-Original-To: freebsd-questions@freebsd.org
Delivered-To: freebsd-questions@freebsd.org
Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125])
	by hub.freebsd.org (Postfix) with ESMTP id 9332416A400
	for <freebsd-questions@freebsd.org>;
	Thu, 23 Mar 2006 15:40:27 +0000 (UTC) (envelope-from steve@camp.com)
Received: from aslan.camp.com (synergy.synergy.dim.com [206.124.12.62])
	by mx1.FreeBSD.org (Postfix) with ESMTP id 392F343D97
	for <freebsd-questions@freebsd.org>;
	Thu, 23 Mar 2006 15:40:04 +0000 (GMT) (envelope-from steve@camp.com)
Received: from aslan.camp.com (localhost [127.0.0.1])
	by aslan.camp.com (8.12.9/8.12.9) with ESMTP id k2NFSZde010148;
	Thu, 23 Mar 2006 08:28:35 -0700 (MST)
Received: (from steve@localhost)
	by aslan.camp.com (8.12.9/8.12.9/Submit) id k2NFSZu9010147;
	Thu, 23 Mar 2006 08:28:35 -0700 (MST)
Date: Thu, 23 Mar 2006 08:28:35 -0700
From: Steve Camp <steve@camp.com>
To: freebsd-questions@freebsd.org
Message-ID: <20060323082835.A9959@aslan.camp.com>
Mime-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
User-Agent: Mutt/1.2.5i
Cc: Steve Camp <steve@aslan.camp.com>
Subject: e-mail relaying without forwarding the entire message?
X-BeenThere: freebsd-questions@freebsd.org
X-Mailman-Version: 2.1.5
Precedence: list
List-Id: User questions <freebsd-questions.freebsd.org>
List-Unsubscribe: <http://lists.freebsd.org/mailman/listinfo/freebsd-questions>, 
	<mailto:freebsd-questions-request@freebsd.org?subject=unsubscribe>
List-Archive: <http://lists.freebsd.org/pipermail/freebsd-questions>
List-Post: <mailto:freebsd-questions@freebsd.org>
List-Help: <mailto:freebsd-questions-request@freebsd.org?subject=help>
List-Subscribe: <http://lists.freebsd.org/mailman/listinfo/freebsd-questions>, 
	<mailto:freebsd-questions-request@freebsd.org?subject=subscribe>
X-List-Received-Date: Thu, 23 Mar 2006 15:40:27 -0000

When one MTA attempts to deliver an e-mail message to another MTA, the
conversation looks something like:

    -> HELO somedomain.com
    <- 250 Hello somedomain.com
    -> MAIL FROM: <sender@somedomain.com>

    <- 250 2.1.0 Sender ok
    -> RCPT TO: <recipient@otherdomain.com>
    <- 250 2.1.5 Recipient ok
    -> DATA
    <- 354 Enter mail
       ...
       <- 250 2.0.0 Message accepted for delivery

My question involves redirecting the sending MTA to a different
receiving MTA.  Rather than the initial receiving MTA having to accept
the entire message (all the DATA) and then forward it on to another
MTA, the initial receiving MTA simply "redirects" the sending MTA to
another MTA -- preferably the MTA that actually handles the e-mail for
"recipient@otherdomain.com".

The conversation that I envision would look something like:

    -> MAIL FROM: <sender@somedomain.com>
    <- 250 2.1.0 Sender ok
    -> RCPT TO: <recipient@otherdomain.com>
    <- XYZ X.W.V Go See someotherserver.otherdomain.com for <recipient@otherdomain.com>

Is such a redirection possible?

Is it hard to configure?

Have I just described "relaying"?

It seems to me that such a "redirect" would be useful (by keeping
bandwidth low on the primary MX for a domain) if an
organization handles such a large volume of e-mail that it has an
"e-mail server farm", or if a geographically disparate organization
has multiple e-mail servers all connected directly to the internet
(well, probably each through a separate firewall).

Regards,

--
Steve Camp
steve@camp.com