Re: [dmarc-ietf] Second WGLC for draft-ietf-dmarc-psd: Definition of NP

[John Levine <[e-mail]>]

In article <[e-mail]> you write:
>Section 2.7. defines a non-existent domain as "a domain for which there is an NXDOMAIN or NODATA response for A, AAAA, and MX
>records.  This is a broader definition than that in NXDOMAIN [RFC8020]." This should be sufficient for determining that the
>domain is not intended to be used and therefore could have a more stringent policy applied.  
>
>The idea of looking for a "mail-enabled domain" based on if an "MX record exists or SPF policy exists" is interesting.
>Although there may be domains that send email but not receive email and so may not have an MX record.

These days I think you will find that if the domains in your bounce
address and your From: headers don't have an MX or A record, very few
recipients will accept your mail. This seems like an edge case. In
practice I find that the domains caught by the Org domain or I suppose
PSD have A records but no mail server because they're actually web
hosts rather than mail hosts.

We have the Null MX to indicate that a domain receives no mail and SPF
plain -all to indicate that it sends no mail so I hope we don't try to
reinvent these particular wheels.

R's,
John