Temporary block of @canonical.com sending to @lists.ubuntu.com

Mark Shuttleworth mark.shuttleworth at canonical.com
Sun Jan 11 11:36:25 UTC 2026


OK, from my perspective then the 'Munge from' option on lists.ubuntu.com
would be a good way forward. Robie?

Mark

On Sun, 11 Jan 2026 at 11:25, Thomas Ward <teward at ubuntu.com> wrote:

> Mark,
> On 2026-01-11 04:44, Mark Shuttleworth wrote:
>
>
> Well this is an interesting conundrum.
>
> Surely every company mail system that does DMARC has this issue with
> mailing lists? Is the mail system @canonical.com doing something unusual?
> It sounds from Robie's description that Canonical is 'just doing DMARC
> conservatively'.
>
> Thanks for any clarification,
> Mark
>
> As I understand the core basis of what's happening, when lists.ubuntu.com
> sends as @canonical.com the message at $RECIPIENT fails DMARC because SPF
> fails.
>
> Unfortunately, this is "normal" with DMARC.  And when DMARC adoption
> became widespread, the traditional concept of "mailing lists" and
> "distribution lists" had to adapt. And that required changing of
> traditional mailing list behaviors.  This is not new, with articles on this
> going back years. (such as [1]).
>
> Most mailing lists that *are* being DMARC compliant follow the 'Munge
> from". So it's not @canonical.com mailing systems at fault, but @
> lists.ubuntu.com mail servers not being in the Canonical.com SPF record.
> Which is probably intentional.
>
> The evolution of email and email security with DMARC has required mailing
> lists to change and adapt like this though. We (Ubuntu and its mailing
> lists) have just never adopted it. And for Robie and me as well, any
> DMARC-failing email (Canonical *or otherwise* over the lists) goes straight
> to junk.
>
> Another prime example of this is Debian's lists - where this happens
> rampantly and results in their (daily) notification of email bounces coming
> to me - because Debian's not allowed to be the sender of emails with From
> addresses which have DMARC enforced.
>
> This is a problem *every* major group running a mailing list has faced.
> And is why the "Munge from" option exists in Mailman to help work around
> the problem.
>
> At my dayjob we run upwards of 50+ specifically-dedicated lists for
> various groups and such whom all are with companies as our partners. A
> large portion of those companies have DMARC enforced on their mail to keep
> up with security and email policies. Every single one of them ended up with
> messages in Junk or Spam (or simply *rejected entirely*) because of DMARC
> not passing on them.
>
> This is why 'traditional mailing lists' are becoming less and less common,
> or are still being used but with munging on the From address in order to
> pass DMARC.
>
>
> Thomas
>
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