[Mono-list] Duplicate emails from list

Jonathan Pryor jonpryor at vt.edu
Mon May 1 06:41:05 EDT 2006

On Sun, 2006-04-30 at 16:03 -0700, Tony G wrote:
> This is exactly the header that I was looking at.  Thank you very much.  I
> completely agree that the TO recipient "might" receive two copies depending
> on mailman and the recipient's MUA.

I suspect that 99.999% of the time, the TO recipient *will* receive two
copies.  It's the sender's MUA which is sending the message, opening an
SMTP connection to one (or more) SMTP servers to transmit the message,
and _that_ server certainly isn't going to know that the TO recipient is
already subscribed to the CC'd mailing list...

Result: the TO recipient will always get two messages, one sent directly
to them, and one indirectly via the mailing list.  It's equivalent to
listing the same email address on both the TO and CC lines.

*Always*.  (Unless the TO recipients MUA looks for duplicate messages
and displays only one...)

Data point: I always get two messages when I'm the TO recipient, one
into my INBOX and one via my Mono filter, as the _headers_ are different
within each message.

For example, the headers for a message sent directly to me:

	Received: from steiner.cc.vt.edu...
	Received: from moutng.kundenserver.de...
	Received: from []...

And the headers for the same message received via the mailing list:

	Received: from steiner.cc.vt.edu...
	Received: from lists.ximian.com...
	Received: from galactus.ximian.com...
	Received: from herald.ximian.com...
	Received: from moutng.kundenserver.de...
	Received: from []...

Is this a bad thing?  I don't think so -- when the mailing list server
is down or otherwise slow (which seems to happen every few months to a
year) it allows the TO recipient to get the message within a reasonable
time frame, as opposed to _days_ later (if the mail server has issues).

> Note however, that I am on the mailman-users list, obviously run using
> mailman, and I do not get dupes from them even when they CC the list.  This
> is why I am so confused about why it's only this one list where this issue
> is manifested.

The question isn't about whether mailman-users is CC'd.  It's about
whether you're the TO recipient _AND_ mailman-users is CC'd -- in which
case I would certainly _hope_ that you get two messages, as you'd be
listed twice (see above SMTP discussion)!

 - Jon

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