[Cake] cake for net-next 4.8

[Toke Høiland-Jørgensen]

Neil Shepperd <nshepperd at 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