[NTG-context] This mailing list is not DKIM (DMARC) compatible

Gerben Wierda gerben.wierda at rna.nl
Tue Sep 17 10:21:40 CEST 2019


Mailman already has settings for this, but one is advised not to use the ‘munging’ option.

My guess is that if you leave the change of body in place, participants that are sending through mail servers that support SPF will fail (because of the resend by the list) and support for DKIM will fail (because of the changed body)

You will still receive the 'list-forwarded’ messages from senders who do not use DMARC, you will start missing those that do. It is unlikely that you will suddenly stop receiving all messages from the list (e.g. mine will go through as I haven’t yet turned DMARC fully on, but as soon as I do, I will be unable to send messages via this list to those at the receiving end that do DMARC checking, and that holds for more and more users.).

The sender’s email manager will also get unnecessary reports of the list server illegally sending messages on their behalf.

Most list these days that I am on already have removed the footer, and leave the Subject: line alone. Sorting can be done on other headers than Subject.

Using dmarc_moderation_action (mailman setting) means that you start to munge headers etc, which is not optimal:

https://begriffs.com/posts/2018-09-18-dmarc-mailing-list.html <https://begriffs.com/posts/2018-09-18-dmarc-mailing-list.html> writes about munging:
However this is a poor use of email, since it’s misrepresenting who originated the message. Also email clients often have a degraded interface with respect to the Reply-To header. It’s usually not visible in the message list, not used for sorting, and not added to the address book.

But whatever you guys do, make sure you are DMARC-proof to prevent running into these issues later on. Either munge, or remove the footer and the change of Subject (I would prefer the latter).

Gerben Wierda
Chess and the Art of Enterprise Architecture <https://ea.rna.nl/the-book/>
Mastering ArchiMate <https://ea.rna.nl/the-book-edition-iii/>
Architecture for Real Enterprises <https://www.infoworld.com/blog/architecture-for-real-enterprises/> at InfoWorld
On Slippery Ice <https://eapj.org/on-slippery-ice/> at EAPJ

> On 16 Sep 2019, at 22:46, Henri Menke <henrimenke at gmail.com> wrote:
> 
> I think this is better reported to Mailman.  I'm not sure to what extent list
> administrators have control over DKIM settings.
> https://gitlab.com/groups/mailman/-/issues
> 
> On 9/17/19 1:34 AM, Gerben Wierda wrote:
>> In addition: Lists should keep the From address, the Subject, and the Message totally unchanged. They should add a Sender header to indicate their relay role, and set at least the List-Id and List-Unsubscribe headers for mailbox rules and subscription management.
>> 
>> 
>> Gerben Wierda
>> Chess and the Art of Enterprise Architecture <https://ea.rna.nl/the-book/>
>> Mastering ArchiMate <https://ea.rna.nl/the-book-edition-iii/>
>> Architecture for Real Enterprises <https://www.infoworld.com/blog/architecture-for-real-enterprises/> at InfoWorld
>> On Slippery Ice <https://eapj.org/on-slippery-ice/> at EAPJ
>> 
>>> On 16 Sep 2019, at 15:21, Gerben Wierda <gerben.wierda at rna.nl <mailto:gerben.wierda at rna.nl>> wrote:
>>> 
>>> The footer that is added to each message in this list is not DKIM (and thus DMARC) compatible. DKIM requires the ability to create a signature on a set of headers and the body. By changing the body, the DKIM signature fails and the resulting messages sent by the mail list may in the future be blocked by  more and more mail servers.
>>> 
>>> Gerben Wierda
>>> Chess and the Art of Enterprise Architecture <https://ea.rna.nl/the-book/>
>>> Mastering ArchiMate <https://ea.rna.nl/the-book-edition-iii/>
>>> Architecture for Real Enterprises <https://www.infoworld.com/blog/architecture-for-real-enterprises/> at InfoWorld
>>> On Slippery Ice <https://eapj.org/on-slippery-ice/> at EAPJ
>>> 
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>> 
>> 
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> ___________________________________________________________________________________
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