Change to Mail Infrastructure - SPF and DKIM verification will now be enforced

Jan Kundr√°t jkt at kde.org
Wed Dec 9 10:51:43 GMT 2015


I've taken the liberty to remove the ad-hominem which you used. I'm not 
happy with your approach to this discussion, but I'll try to stick with the 
technical points.

There is active work within the DMARC WG, with first drafts being published 
only *two months ago* [1]. My suggestion for everybody who doesn't have 
time to follow this process is to sit back, relax, and watch the IETF come 
up with a solution, and *then* start implementing their suggestions. Asking 
one's user base to reach every list service administrator out there with a 
"fix your DKIM/DMARC" is not going to work. Deploying DMARC at this point 
in time, when substantial changes are still being worked on, doesn't look 
like a good idea, either. This is all that I'm saying.

> The mailing list hosts don't have to deploy DKIM. All they have to do
> is not break signatures on mails bearing a DKIM signature.
> Which, as I noted in my email is something that only requires a few
> toggles within the Mailman administration interface.
> (And, using the withlist tool can be changed on all lists on an entire
> server with relative ease). This is what Debian has chosen to do.

You're saying that it's easy to configure a ML to stop breaking DMARC 
signatures. I disagree. Here's my reasoning:

1) Full compliance with DMARC requires a substantial reduction of features 
which distinguish mailing lists from dumb forwarders. This includes:

- the Reply-To munging,
- adding a [prefix] to subject headers,
- automatic signatures,
- in case of overly strict DKIM setup, the various List-* headers which are 
actually mandated by RFCs to be automatically added.

2) Some domains might specify DMARC policies which prevent *any* 
distribution of their e-mails over mailing lists. The only solution for 
this problem is rewriting the RFC5322.From header to something like:

 From: "Foo Bar via a KDE ML" <kde-ml at lists.kde.org>

This in turns leads to e-mails where one cannot reply to the original 
author anymore, etc etc etc.

In case someone is still following this thread, let me quote [2] John R. 
Levine, one of the Internet graybeards:

> Mailing list apps can't "implement DMARC" other than by getting rid of every feature that makes lists more functional than simple forwarders. Given that we haven't done so for any of the previous FUSSPs that didn't contemplate mailing lists, because those features are useful to our users, it seems unlikely we'll do so now.
> 
> If receivers want to implement DMARC policy, they need to make their false alarm whitelist first. This appears to be a substantial, perhaps insurmountable, hurdle.

"FUSSP" is a "Final Ultimate Solution to the Spam Problem".

That entire thread is worth reading, btw.

Cheers,
Jan

[1] https://tools.ietf.org/html/draft-andersen-arc-00
[2] http://www.ietf.org/mail-archive/web/ietf/current/msg87157.html

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