[Mailman-Users] DMARC issues
barry at list.org
Thu Apr 10 17:36:16 CEST 2014
On Apr 10, 2014, at 03:09 PM, Siniša Burina wrote:
>I believe there's no need to elaborate on the problems recently introduced by
>Yahoo, changing their DMARC DNS record and rendering many mailman lists
>unusable for Yahoo mail users.
It *is* a shame that these anti-spam defenses knowingly break mailing lists.
I say "knowingly" but not "maliciously" because their specs usually describe
the adverse affects on mailing lists, along with some mitigation approaches
(which may not have a positive effect on list usability <wink>). The spec
authors are not hostile to mailing lists and would rather not break them, but
there does seem to be a fundamental conflict between mailing lists and
That said, DMARC was discussed in great detail last year on the -developers
list, so if you want all the gory details, check out those archives.
Mark will probably follow up in more detail, but MM2.1 implemented a feature
in 2.1.16 called "from_is_list" which is a ternary option for addressing the
effects of DMARC. It has to be enabled by the site admin, and then list
admins can opt-in. It's disabled by default for backward compatibility
reasons. From Defaults.py:
# The following is a three way setting.
# 0 -> Do not rewrite the From: or wrap the message.
# 1 -> Rewrite the From: header of posts replacing the posters address with
# that of the list. Also see REMOVE_DKIM_HEADERS above.
# 2 -> Do not modify the From: of the message, but wrap the message in an outer
# message From the list address.
DEFAULT_FROM_IS_LIST = 0
So as you can see, two approaches are available, From: rewriting or outer
message wrapping. Both are suboptimal for usability, but it seems like we
have no other viable option. This is not yet implemented in MM3 because I
don't really like having to do it. We might have no choice though.
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