[Mailman-Users] DKIM, SPF, DMARC, Mail_as_list all working, but MUAs not happy

Mark Sapiro mark at msapiro.net
Tue Apr 5 16:00:41 EDT 2016

On 04/05/2016 12:14 PM, Arlen Raasch wrote:
> A large number of our users are not happy with how mail is presented when
> Mail_as_list is active.  They messages appear as attachments in some MUAs.
> If I change from Mail_as_list to Mung From, DKIM does not validate.

I'm guessing you are talking about the from_is_list setting and you are
using 'Wrap Message'.

> I noticed from previous emails I received from this list that DKIM does not
> validate here either.

The original, incoming DKIM signature doesn't validate because list
transformations such as prefixing the subject or adding msg_footer break
the sig.

I just checked and found that mail.python.org was not DKIM signing
outgoing list mail because it was checking only the From: domain for
python.org. I have hopefully just corrected that.

> Can I just switch the list to Mung From with some certainty that the email
> providers will continue to relay our traffic as we have valid SPF and DMARC
> records?

If Wrap Message is currently working for you, I don't know why Munge
>From would not work, but there is little difference between these
actions in Mailman 2.1.21 vs 2.1.16. However, 2.1.21 does offer
dmarc_moderation_action so you can apply Wrap Message or Munge From only
to those messages which are From: a domain which publishes a DMARC
p=reject (and optionally p=quarantine) policy.

> Would switching to a later version of mailman make this any better (and
> why)?

Maybe. As I say above, it would allow you to only apply DMARC
mitigations to those posts that need it. Whether it would make Munge
>From any better depends on what the current issue is. I know of no
reason why Wrap Message would be effective in avoiding DMARC rejects and
Munge From would not, but ISPs do funny things and are secretive about
it, so who knows.

My own lists and the python.org lists do Munge From and we don't see
DMARC bounces.

Mark Sapiro <mark at msapiro.net>        The highway is for gamblers,
San Francisco Bay Area, California    better use your sense - B. Dylan

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