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Re: Your setting Return-Path to YOU in your cygwin@cygwin postings

I thank you both for enlightning me on this subject.

I'm using the Thunderbird email client. I have observed that it is wrongly using the "Return-Path" and not the "Reply-To" even in the email composing phase before the ISP gets involved. I'll watch that more or seekout a RFC compliant email client.

Just doing a "Reply" is definitely NOT an automated response. Thanks for the unblock.

Thanks, Paul

Thunderbird Version (20081209)

Dave Korn wrote:
[ This is completely off-topic, so moved to the proper list. ]
Paul McFerrin wrote:

I examined your email headers and discovered that in your postings to cygwin ARGH DO NOT POST EMAIL ADDRESSES TO THE LIST, you are
setting "Return-Path: <dave.korn.cygwin PCYMTNQREAIYR>" in
your email header so naturally everyone who is "replying" to sender will be
sending YOU their reply, not cygwin ARGH This could explain why you
are getting so much direct replies.

That's not actually what's happening. Here is the raw text of my most recent list posting at sourceware:

As you can see there is no such header. Here are a few others; likewise.

  Notice how the Return-Path in all of these posts is a munged version of the
list subscriber name, as should be the case in all posts sent out by the
sourceware mailing lists; that way, if mail bounces, it is returned to the
list daemon, which can find out which list subscriber is bouncing and stop
sending messages if they carry on bouncing them for too long.

  Note also how all those paths have a Mail-Followup-To header pointing at the
list.  Any mailer that does not respect that when you hit Reply is broken and
does not comply with internet standards.  The Return-Path is for automated
error messages *only*, not replies of any sort.

  Also, here is a screenshot of my email settings, where I do not have any
Reply-To header set:

  You'll just have to take my word for it that I haven't changed them since
you suggested this, although the historical record of my posts in the archive
backs me up on this.  Here also are the headers of one of the posts in my
local sent items folder (modulo obvious anti-spam munging)

>From - Tue Mar 03 23:15:26 2009
X-Mozilla-Status: 0001
X-Mozilla-Status2: 00800000

Message-ID: <>
Date: Tue, 03 Mar 2009 23:15:25 +0000
From: Dave Korn <dave SPOT korn SPOT cygwin SPLAT gmail SPOT com>
User-Agent: Thunderbird (Windows/20080914)
MIME-Version: 1.0
To: cygwin SPLAT cygwin SPOT com
Subject: Re: concurrent use of cygwin1.dll for 1.5 & 1.7 ??
References: <>
In-Reply-To: <>
Content-Type: text/plain; charset=ISO-8859-1
Content-Transfer-Encoding: 7bit

corresponding to the message mentioned previously at

Note that it also has no return-path header.

  Also, to see how the email headers look when they're received downstream
from sourceware, I went to gmane to look for the same post there.

From: Dave Korn <dave SPOT korn SPOT cygwin SPLAT googlemail SPOT com>
Newsgroups: gmane.os.cygwin
Subject: Re: concurrent use of cygwin1.dll for 1.5 & 1.7 ??
Date: Tue, 03 Mar 2009 23:15:25 +0000
Lines: 17
Approved: news SPLAT gmane SPOT org
Message-ID: <>
References: <>
Mime-Version: 1.0
Content-Type: text/plain; charset=ISO-8859-1
Content-Transfer-Encoding: 7bit
X-Trace: 1236121596 6607 (3 Mar 2009 23:06:36 GMT)
X-Complaints-To: usenet SPLAT ger SPOT gmane SPOT org
NNTP-Posting-Date: Tue, 3 Mar 2009 23:06:36 +0000 (UTC)
To: cygwin SPLAT cygwin SPOT com
Original-X-From: cygwin-return-148486-goc-cygwin=m SPOT gmane SPOT org SPLAT
cygwin SPOT com Wed Mar 04 00:07:52 2009
Return-path: <cygwin-return-148486-goc-cygwin=m SPOT gmane SPOT org SPLAT
cygwin SPOT com>
Envelope-to: goc-cygwin SPLAT gmane SPOT org
Original-Received: from ([])
	by with smtp (Exim 4.50)
	id 1LediC-0006oG-50
	for goc-cygwin SPLAT gmane SPOT org; Wed, 04 Mar 2009 00:07:44 +0100
Original-Received: (qmail 15139 invoked by alias); 3 Mar 2009 23:06:14 -0000
Original-Received: (qmail 15131 invoked by uid 22791); 3 Mar 2009 23:06:13 -0000
X-SWARE-Spam-Status: No, hits=-2.4 required=5.0 	tests=AWL,BAYES_00,SPF_PASS
Original-Received: from (HELO
(     by (qpsmtpd/0.43rc1) with ESMTP; Tue, 03
Mar 2009 23:06:07 +0000
Original-Received: by with SMTP id 26so497818eyw.20
     for <cygwin SPLAT cygwin SPOT com>; Tue, 03 Mar 2009 15:06:04 -0800 (PST)
Original-Received: by with SMTP id
p1mr1670744ebc.9.1236121564306;         Tue, 03 Mar 2009 15:06:04 -0800 (PST)
Original-Received: from ?
( [])         by with ESMTPS id k9sm10716748nfh.62.2009.
(version=SSLv3 cipher=RC4-MD5);         Tue, 03 Mar 2009 15:06:04 -0800 (PST)
User-Agent: Thunderbird (Windows/20080914)
In-Reply-To: <>
Mailing-List: contact cygwin-help SPLAT cygwin SPOT com; run by ezmlm
Precedence: bulk
List-Id: <>
List-Unsubscribe: <mailto:cygwin-unsubscribe-goc-cygwin=m SPOT gmane SPOT org
List-Subscribe: <mailto:cygwin-subscribe SPLAT cygwin SPOT com>
List-Archive: <>
List-Post: <mailto:cygwin SPLAT cygwin SPOT com>
List-Help: <mailto:cygwin-help SPLAT cygwin SPOT com>,
Original-Sender: cygwin-owner SPLAT cygwin SPOT com
Mail-Followup-To: cygwin SPLAT cygwin SPOT com
Delivered-To: mailing list cygwin SPLAT cygwin SPOT com
Xref: gmane.os.cygwin:104617
Archived-At: <>

  As before, you can see that the return path is the proper bounce address for
auto-unsubscribing, and the Mail-Followup-To points to the list.

So, I trust there is no doubt that at least one of us knows how to drive a mailer. However, I'm willing to take your word for it that you have experienced some kind of confusion or misunderstanding at your end through no malicious intent of your own. It strikes me that you could be the innocent victim of a buggy mail server at your ISP. (Come to think of it, this is RR we're talking about; it would be a surprise if you /weren't/ suffering from lousy servers at your ISP....) You were unlucky to be the 'n'th person in a row to mail me and be there at just the point when I lost patience, but I don't suppose they all have faulty ISP mailservers.

The text in RFC5321 that defines the Return-Path header is as follows:

When the delivery SMTP server makes the "final delivery" of a
   message, it inserts a return-path line at the beginning of the mail
   data.  This use of return-path is required; mail systems MUST support
   it.  The return-path line preserves the information in the <reverse-
   path> from the MAIL command.  Here, final delivery means the message
   has left the SMTP environment.  Normally, this would mean it had been
   delivered to the destination user or an associated mail drop, but in
   some cases it may be further processed and transmitted by another
   mail system.


  What this implies is that the bogus Return-Path header must have been
generated at your ISP mailserver, and I can guess what it's doing wrong: it's
using the address in the From: line in the email (rfc822) headers, rather than
the address in the "MAIL FROM" command when it receives the email from, which will be presenting as the munged version
containing the subscribed user's address.

  So, I see that you are the victim of an unfortunate accident, although I
maintain that sending me the same request twice five minutes apart was a bit
pushy.  I've unblocked your address; please remember that, through no fault of
your own, you'll have to take more care in future.


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