[Mailman-Users] Can't hide sender of message

[Stephen J. Turnbull]

TomSherlock writes:

 > They receive two messages, one from the list and one from the poster.
 > 
 > Here is the header from the poster:

Cutting to the chase, from poster, the (relevant, edited) headers are:

 > Received: from a2s47 by m1pismtp01-023
 > Received: from smtp1 by a2s47

>From list:

 > Received: from vms169129pub by p3pismtp01-026
 > Received: from a2s47 by vms169129 for tom at ramruva.com (ORCPT tj.sherlock)
 > Received: from localhost by a2s47
 > Received: from smtp1 by a2s47

First, note the "from localhost" entry in the second series.  This
means that Mailman is reinjecting the message on the same host.  It
doesn't appear in the first series; Mailman did *not* handle that
message, it was relayed *directly to you* by the MTA at a2s47.
Second, apparently the list knows you as "tj.sherlock at verizon", but
it's likely the direct mail was originally addressed to "tom at ramruva".

I would guess that the sender is BCC'ing you (perhaps to help you
identify any problems?)  It's hard to say because I don't know
Microsoft Exchange, but it is quite possible that the mail from the
sender's host is going to multiple recipients (ie, other than the
list) at the point where her MUA injects it.  If there were a single
message to the list only, the first MTA in the chain will often have a
"for mailing-list" clause in the Received header.  Its absence doesn't
prove anything, but certainly leaves open the possibility of multiple
recipients.

A lower probability is that there's a rule or alias at a2s47's MTA
that BCCs you on list mail, again for debugging purposes.
(Coincidentally, yesterday I implemented exactly that feature using
the same MTA (Exim 4) for a list I run, although the purpose was
different.  It's just one line in /etc/aliases.)

As unlikely as that seems, based on the Received chain posted, I would
say a problem with Mailman is even less likely.  I just don't see how
Mailman could be involved with the direct mail.

I'm sorry we can't find a Mailman issue here, in the sense that we
could help you with that.