[Mailman-Users] Yahoo Groups' From munging and X-Original-From

Richard Damon Richard at Damon-Family.org
Sun May 25 19:48:01 CEST 2014

On 5/25/14, 11:48 AM, Mark Rousell wrote:
> What do you think of Yahoo Groups' From munging style and their
> X-Original-From header?
> Here is an example:
> X-Original-From: Mark Rousell <markr at signal100.com>
> From: "Mark Rousell markr at signal100.com [some-mail-list]"
> 	<some-mail-list at yahoogroups.com>
> I feel this is one of the better combinations of munging and new
> headers. All the information is there (and is very clear) and the
> X-Original-From header could (in due course) be recognised by mail
> clients and mailing list archive software.
> I realise that this falls foul of
> http://www.dmarc.org/supplemental/mailman-project-mlm-dmarc-reqs.html
> and yet it does seem to offer many benefits, especially the
> X-Original-From header and the promise it holds for automated recognition.
> It is also possible to add X-Original-From to the .INVALID/.REMOVEME
> munging that some prefer too:
> X-Original-From: Mark Rousell <markr at p-reject-domain.com>
> From: "Mark Rousell [via some-mail-list]"
> 	<markr at p-reject-domain.com.REMOVEME>
> Any thoughts?
My view is that any attempt to have the Mail User Agent show a message
that went through a mailing list as if it originated from the original
poster (and only from that poster) is doomed, because the whole point of
DMARC, is that domains that that are using DMARC are indicating that
email that appears to be from their domain is only supposed to get to
you from that domain, and others aren't supposed to be able to
masquerade as it. If mailing list could do it, so could phishers. And if
this became somewhat common, DMARC, to achieve its goal of confirming
sender identity would need to add checking that.

The only possible option for that would be wrapping, where the wrapped
message was EXACTLY as sent (thus no content filtering, and all
additions are added to the wrapper, not the original message).

The problem we are seeing is that we have domains that don't really need
that restriction are using it, and the world is needing to figure out
how to make this work.

The real solution, in my opinion, would be a standard that deals with
how MUA display the senders of messages, and a system similar to https
certificates where domains (or email addresses) that really need
verification could get a certificate and be able to have their addresses
displayed a "verified", email pretending to be from them but not
properly signed could be rejected or marked suspicious, but most
personal mail would just be unverified.  It should make it clear that
any ESP that uses this has an obligation to let is users understand the
rules, and that it users are not allowed to let 3rd parties (like
mailing list or other 3rd party mailers) send on their behalf (unless
the standard allows a given email address to provide a cert to a 3rd
party it indicate they are an authorized remailer for them). This should
deal with the phish problem, at least once people are taught to look for
the verified icon from "important" sources.

Richard Damon

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