PSA: Mailman changes, From addresses no longer accurate

Дилян Палаузов dpa-libreoffice at
Wed Mar 13 11:48:52 UTC 2019


mailman behind libreoffice at currently does not rewrite the From: header in DMARC-protected domains
(with policy reject or quarantine), despite the statement below.

Emails from such domains spread over the mailing list libreoffice at just don’t reach the recipients,
if the recipients honour DMARC.  Every self-respecting email provider honours DMARC on incoming emails.

Examples of such messages are:

Date: Tue, 12 Mar 2019 20:21:44 +0000 (UTC)
From: Joseph Landry Bougang Fotso <jlandry476 at>
To: <libreoffice at>
Message-ID: <430875294.6291091.1552422104235 at>
Subject: Source code

From: Christian Lohmaier <lohmaier at>
Date: Tue, 12 Mar 2019 13:30:00 +0100
Message-ID: <CAOPHaVTHunJpJYAX=0hdWX16GWSVCZ14v4ucFjeKRMZVJNEJnw at>
Subject: Re: git Push to online project
To: ahmed elshreif <ahmedtota29 at>
Cc: libreoffice-dev <LibreOffice at>

Date: Thu, 7 Mar 2019 10:10:05 +0000 (UTC)
From: Joseph Landry Bougang Fotso <jlandry476 at>
To: <libreoffice at>
Message-ID: <252397585.1361268.1551953405875 at>
In-Reply-To: <mailman.33.1551873602.27620.libreoffice at>
References: <mailman.33.1551873602.27620.libreoffice at>
Subject: Introducing myself and question


On Tue, 2019-02-12 at 11:13 +0100, Michael Meeks via LibreOffice wrote:
> Hi everyone,
> 	Just to make everyone aware of some of this change. The punch-line is
> simple: beware of re-written From: and Reply-To: headers - and check
> that your mail is going to whom you think it is.
> 	The behavior will differ depending on the sending domain so - somewhat
> counter-intuitive.
> 	Just the messenger ;-)
> 		Michael.
> ---------- Forwarded message ---------
> From: Daniel Stone <daniel at>
> Date: Mon, 11 Feb 2019 at 23:38
> Subject: PSA: Mailman changes, From addresses no longer accurate
> To: <freedesktop at>,
> <sitewranglers at>
> Hi all,
> We have hit another step change in aggressive anti-spam techniques
> from major mail providers. Over the past few days, we saw a huge spike
> in the number of mails we were failing to deliver to GMail and
> in particular.
> It looks like it is now no longer acceptable for us to break
> DMARC/DKIM/SPF. These are DNS-based extensions to SMTP, which allow
> domains to publish policies as to who should be allowed to send email
> on their behalf. SPF provides source filtering, so e.g.
> could specify that no-one should accept mail with a
> From: * unless it came from
> Mailman completely breaks this: if I specified a filter only allowing
> Google to send mail for, then anyone enforcing SPF
> would reject receipt of this mail, as it would arrive from fd.o with
> my From address.
> DKIM allows domains to publish a public key in DNS, inserting a header
> into mails sent from their domain cryptographically signing the value
> of named headers. Mailman breaks this too: changing the Sender header
> (such that bounces get processed by Mailman, rather than sending a
> deluge of out-of-office and mailbox-over-quota messages to whoever
> posts to the list) can break most DKIM signatures. Mailman adding the
> unsubscribe footer also breaks this; we could make it not add the
> footer, but in order to do so we'd have to convince ourselves that we
> were not decreasing our GDPR compliance.
> DMARC ties the two together, allowing domains to specify whether or
> not DKIM/SPF should be mandatory, and if they fail, what action should
> be taken. Despite some domains specifying a fail action of 'none'
> (receiving MTA to send an advisory report to a named email address,
> but still allow the email), it seems that popular services still
> interpret 'none' as 'reject'.
> As a result, Google in particular is dropping some number of our mails
> on the floor. This does _not_ just apply to mails which fail
> DMARC/DKIM/SPF: every mail we send that fails these filters (which is
> a lot - e.g. Intel and NVIDIA both have SPF) decreases our sender
> reputation with GMail and causes it to reject legitimate mails.
> I've reached out to Google through a couple of channels to see what we
> can do to increase our delivery rate to them. In the meantime, if your
> mail is hosted by Google, or Outlook, and you think you're missing
> mails - you probably are.
> Mailman has also now been reconfigured such that if it spots a
> potential DMARC violation, it rewrites the From address to be
>, keeping the original author in Reply-To. It
> also strips DKIM headers. This seems to be about the best we can do,
> unless and until the major mail service providers offer us some
> alternate way to send mail. If you are replying privately to someone,
> you should check very carefully that you are replying to them and not
> to the list.
> Unfortunately we don't have a good answer in the long run. The latest
> published RFC at suggests that
> there are no good solutions. If anyone is blessed with an abundance of
> time and familiar with the current email landscape, I would love to
> talk to you and get your help to work on this. Unfortunately we don't
> have the manpower to actually properly monitor email; it can often
> take a collapse in successful-delivery rates for us to notice.
> Ultimately, I suspect the best solution is to move most of our
> discussions to dedicated fora like GitLab issues, or something like
> Discourse. Fundamentally, the thing we're trying to do (send email to
> thousands of people at a time using a fake From address) is ... kind
> of the opposite of what the 2019 Internet wants us to do. Every few
> months the major providers drop more of our mail as they become more
> aggressive with spam, and every few months their userbase increases by
> a non-trivial amount.
> We've done a lot of work on our email infrastructure, and are doing
> our best to be a responsible citizen within the constraint of having
> to launder mail and forge identity on an industrial scale, but it's
> coming to the point where it just may not be possible to run such a
> service at such a scale anymore.
> This is before even considering our other issues with Mailman 2.x: no
> centralised identity management (mailing your passwords out every
> month ... ?!), difficulty of GDPR compliance (editing archives
> requires hand-editing every single HTML index, as there is no
> non-destructive archive rebuild), the flat-out bugs (e.g. the mesa-dev
> archives are usually missing half the messages), and the fact it's
> been abandoned upstream in favour of Mailman 3.x, which is not
> obviously better, nor is there a clear upgrade path to.
> Of course we do not have any plans to stop providing email any time
> soon, but it might be worth thinking about what you can do to reduce
> your dependency on email lists. At the current rate of degradation, it
> might be non-viable quicker than you'd think. Maybe this is unduly
> gloomy, but the entire internet's direction of travel has been away
> from services like Mailman, and its velocity is only increasing.
> Cheers,
> Daniel
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