thank you, Yahoo

[Dirk Hohndel]

> On Jul 13, 2016, at 1:49 AM, Linus Torvalds <torvalds at linux-foundation.org> wrote:
> 
> 
> On Jul 12, 2016 17:05, "Dirk Hohndel" <dirk at hohndel.org <mailto: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.
> 

So all the bounces that caused the unsubscribes were DMARC failures. Specifically, the From: field was a yahoo.com address, but of course my mail server (which sends out the mailing list email) is not a valid sender for yahoo.com, so the servers who follow the DMARC reject policy (like Yahoo’s own server and those of outlook.com, hotmail.com, and the various Yahoo domains I mentioned.

This is NOT related to DKIM.

/D
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