** Sometime around 20:32 -0600 11/29/01, Winship said:

>On Thu, 29 Nov 2001, Randy Ryan wrote:
>  > Exactly what portion of the header in a listserv email donates the bounce
>  > address?

The address shown in the "Return-Path:" header is the bounce address.

Technically, however, the bounce address is specified in the MAIL
FROM transaction during the SMTP session -- that is, in the message's
"envelope" (hence, the reason that MAIL FROM is often referred to as
"envelope from"). Note that this address is passed in the SMTP
session, and is not part of the header; specifically, it is *not* to
be confused with the "From:" address in the header.

When the message passes from the SMTP system into any other system
(spooled out to disk, gatewayed to another mail system, etc.), the
MAIL FROM address is, at that time, promoted into the SMTP header as
the "Return-Path:" address.

Thus, to answer your question, the Return-Path: address in the SMTP
header will contain the "bounce address." However, not all systems
promote MAIL FROM to the Return-Path: line, so the line is not always
present. And, more importantly, many systems do not honor the
Return-Path: line -- that is, they do not bounce mail to the
envelope-from address. Which leads me to....

>That rather depends upon how the subscriber's system chooses to misread
>the header.   :-)     Douglas

This is entirely true. There are some MTAs (mail servers) that will
bounce mail to header From:, and there are some that will bounce mail
to Reply-To:. Some MTAs -- mostly older ones -- will honor Errors-To:
when present. I would say that these practices violate the relevant
RFCs, but (unfortunately) the RFCs do not _require_ that mail be
bounced to the return-path, they merely recommend it. (I believe that
this is still the case with 2821/2822.) Nevertheless, MTAs that
bounce to anything other than the return-path are generally
considered within the community to be brain-dead.

To be sure, there is no harm in bouncing to Errors-To: when present
(this is merely my opinion, others may/will disagree, and I generally
do not take issue with their comments regarding Errors-To:), so, IMO,
it is generally safe to include an Errors-To: header in your outbound
mail to "catch" those MTAs that look for it. (They are well in the
minority.)

Far more dangerous is bouncing to header From: or Reply-To:. In these
cases, individual subscribers who post to, for example, discussion
lists may receive bounces from other subscribers' MTAs. I generally
remove the subscribers whose MTAs are misconfigured; if they try to
return to the list, I request that they subscribe through a different
server, such as Hotmail or Yahoo!Mail.

I hope that this was reasonably clear. Let me know if i wasn't, and
I'll be happy to provide clarification.


__________________________________________________________________________
Vince Sabio                                                  [log in to unmask]