> On Jul 13, 2016, at 1:49 AM, Linus Torvalds <[email protected]> 
> wrote:
> 
> 
> On Jul 12, 2016 17:05, "Dirk Hohndel" <[email protected] 
> <mailto:[email protected]>> 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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