[Mailman-Users] non-subscriber managed to post to a subscriber only list

[Lindsay Haisley]

On Tue, 2009-01-27 at 09:25 -0600, Grant Taylor wrote:
> I can see how altering your From (depending on where you are sending to) 
> could be a possibility.  Though I think that the MTA sending out as 
> <user>@<host>.<domain>.<tld> is a mis-configuration on the MTA's part. 
> As far as the Sender: header, I can see that, thus I refine my statement 
> such that either the (preferably) From: or the Sender: headers should 
> match the SMTP envelope sender / Return-Path: header.

Please see Sec. 3.6 of RFC 2822 for a full discussion of various e-mail
header fields and their proper uses and meanings, and RFC 2821 for a
discussion of the trace fields, such as Return-Path.  It is not a
misconfiguration of a MTA for for the envelope sender to be of the form
"<user>@<host>.<domain>.<tld>" as long as this is a working address.
Mail systems which are unable to deliver a received email are required
to use the Return-Path address (the SMTP envelope sender address) to
which to send DSNs and NDRs.

All the header fields which we're discussing here have very precisely
defined uses, and the nuances of these field definitions are, I believe,
somewhat OT for this list.  IMHO, it would be an error to try to force
any of these fields to match one another without fully understanding
their intended uses.  There is, unfortunately, way too much of this sort
of thing these days as people writing email management software,
including some pretty big players, have played fast and lose with the
RFCs and have muddied the waters for the rest of us who are trying to
make the Internet email system work cleanly and reliably.

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