Re: [mlmmj] Mailing Lists and DKIM signing breaking when sender DKIM policy is REJECT

Hi Christof,

Thanks for the reply - and yes, it's From-munging that I'm wanting to be =
able to do.


I want to be able to:
1) Insert [ListName] into the start of the subject.
2) Make it so when someone uses 'Reply' (not Reply-All), that their =
reply comes back to the list by default. This means either the 'From' or =
'Reply-To' has to be set to the list address.

However doing either/both these actions is invalidating the original =
senders dkim and then its delivery is dependant on the dmarc policy of =
the original user (and anything other than a policy of none means =
delivery isn't guaranteed).


The guide you referenced highlights the issue.

1) If mlmmj just passes on the message unmodified, then the original =
senders dkim is checked (and should pass).

2) if mlmmj modifies the subject and/or adds another header (eg =
Reply-To:) then depending on the original senders dkim criteria (eg. =
Google includes Reply-To in their dkim signature) will fail in this =
case.  And when it fails, it may send or not depending on their DMARC =
policy.
This is exactly what was happening in our case.



I note this mailing list:

1) Modifies the 'Subject' by inserting [mlmmj] at the start - this will =
invalidate the original senders dkim.

2) Sets the 'Sender:' header, however this didn't make any difference =
when I used 'Reply'  It wasn't until I clicked 'Reply All' that the list =
was added as a recipient (and the Cc recipient) and hence why I was =
originally setting the 'Reply-To:' header.



What's the process to request a flag to make this option available ?

As much as I avoid Google myself, the enforcing by Google and Yahoo of =
SPF, DKIM and DMARC means you are needing to do what they do like it or =
not, and their own mailing lists are From-munging !


Cheers
Kent



> On 8 Apr 2024, at 6:23=E2=80=AFPM, Christof Thalhofer =
<[email protected]> wrote:
>=20
> Am 08.04.24 um 07:32 schrieb Kent:
>=20
>> The only thing I haven't worked out is how to insert the original
>> senders name into the 'From' so each message at least looks like it
>> came from someone different.
>> Anyone have any ideas on how I can achieve this last bit in the
>> puzzle ?
>=20
> Mlmmj cannot do From-munging. But if you don't break DKIM-Signatures =
by altering headers like From, Subject, Body and Reply-To the mails from =
your mailinglist will be accepted.
>=20
> https://begriffs.com/posts/2018-09-18-dmarc-mailing-list.html
>=20
> Alles Gute
>=20
> Christof Thalhofer
>=20
> --=20
> Dies ist keine Signatur
>=20
>=20
>=20