Huh?   The design is fine:   check the exact match domain and then move up
to N if more than N labels.

The N applies to both original and secondary walks

I have legitimate messages with exact match on 6 labels, so there is no
reason to disavow the ability to put a policy at that level or to disavow
finding an organization at all.



On Sat, Apr 20, 2024, 10:55 PM John Levine <[email protected]> wrote:

> It appears that Scott Kitterman  <[email protected]> said:
> >> Or I suppose say if there's more than 8 components in the name, just
> stop
> >> because no domain actually used for mail is that deep.  Take out the
> skip
> >> stuff.
> >
> >I am not entirely unsympathetic, but I think what we have is reasonable
> and
> >based on Todd's message that I just replied to, I think we can leave it
> as is
> >with some additional discussion.  I prefer we define the constraint
> (however we
> >do it) so that record publishers can have some common expectation of what
> >DMARC receivers will do.
> >
> >My experience with these kinds of things is that if we don't define the
> DOS
> >constraints in the protocol where we've identified a potential issue
> there will
> >be problems in implementation ranging between those the make an overly
> narrow
> >constraint to those the believe that since the constraint isn't in the
> RFC,
> >it's not allowed.
>
> So how about we take out the tree walk and say that if a name has more
> than 8 components, don't do the tree walk and you never find an org
> domain. I suppose this means the bad guys would send mail from
> [email protected], which would now have no policy
> but there's other reasons to reject names like that, most notably that
> the name doesn't exist in the DNS.
>
> If people really have seen mail domains with more than 8 components,
> make it 10 or whatever.
>
> I don't think I've ever seen a useful domain with more than 8
> components other than IPv6 rDNS and DNSBL which don't count.
>
> R's,
> John
>
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