Hmm, PTR record is there, so I guess setting up DKIM is indeed the most
likely culprit.

On 30 September 2016 at 04:02, Toke Høiland-Jørgensen <toke@toke.dk> wrote:

> Neil Shepperd <nshepperd@gmail.com> writes:
>
> > I think I have now accumulated enough spam/nonspam classified emails
> > to make a statistically signification observation: it seems like all
> > emails classified as spam from these lists were send from ipv6:
> >
> > SPF: PASS with IP 2600:3c03:0:0:f03c:91ff:fe61:86ce
> >
> > All emails from bufferbloat.net lists are failing DKIM (because of the
> > mailing list footer breaking the DKIM signature) which might be worth
> > fixing, and failing DMARC because all mailing lists fails DMARC
> > (however google does not have a strict DMARC policy so that shouldn't
> > matter, I hope).
> >
> > By the way, it's not just you, either. I have emails from others on
> > these lists in my spam folder.
> >
> > The distinguishing factor seems to be whether the email was sent from
> > the lists.bufferbloat.net ipv6 address. Unless this address
> > corresponds to some kind of tunnel broker possibly also used by
> > spammers, I can only assume this is some kind of bug (after all, it
> > was spf validated so the address shouldn't matter at that point?).
>
> Indeed, gmail requires extra measures for IPv6:
> https://support.google.com/mail/answer/81126 (scroll down to "Additional
> guidelines for IPv6").
>
> Fixing DKIM might be worthwhile :)
>
> -Toke
>