thank you, Yahoo

Linus Torvalds torvalds at linux-foundation.org
Tue Jul 12 09:49:05 PDT 2016


On Jul 12, 2016 17:05, "Dirk Hohndel" <dirk at hohndel.org> wrote:
>
> Yahoo's strict DMARC policies cause mail that is sent through mailing
> lists that don't rewrite the From: header (like ours) to fatally bounce
> when someone with a Yahoo email address (like Axel) sends email to such a
> mailing list.

So I suspect what is happening is that because subsurface adds the mailing
list footer to the email body, that in turn makes the DKIM body hash
verification fail.

End result: the email looks spoofed.

So what you could try first is to make sure the mailing list doesn't change
anything in the email. Try disabling the body rewriting.

Rewriting the from field avoids the problem because the sender is used to
look up what the policy for that sender is, and yahoo not only indicated
that yahoo emails are DKIM protected, but has a hard failure policy, I
think.

But rewriting the sender is a worse "fix" than the problem it fixes. It's
just the wrong workaround.

The kernel mailing list stopped rewriting the email body. There are still
DMARC failures, but the ones I've seen are about the sender using the wrong
SMTP server and not getting the DKIM signatures at all. So then it's simply
a sender setup problem.

    Linus
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