Re: [dmarc-ietf] what to document about the tree walk

[John Levine <[e-mail]>]

It appears that Murray S. Kucherawy  <[e-mail]> said:
>There is indeed more of a burden on sending domains and registry operators
>to publish the needed markers in the DNS before this will all work the way
>we want it to. ...

Not really. If a mail sender has a DMARC record at its org domain, and
there are no DMARC records above the org domain, things will work
correctly, no psd tag needed. I expect that in practice this will
happen 100% of the time, rounding to the closest 0.01%.  That's why
it is not a problem that popular TLDs like .com, .org, and .net will
never publish a DMARC record, with or without psd=y.

There are at least 200 million registered domains but less than 10000
domains in the PSL. For PSDs, we are talking about one domain in
20,000, or about 0.005% of registered domains. 

Having surveyed all of the domains in the PSL to see which ones
publish DMARC records, I can report that the ones where the lack of a
psd tag might plausibly cause problems can be counted on your fingers.
Some of those already have np= tags which tells us they're aware of
what's going on. (See for example _dmarc.uk.com.)

The tree walk works fine. The psd tag is an arcane nit, mostly useful
to a handful of TLDs like .bank and .insurance that want to use the
aggregate reports to audit their registrants' mail configuration.

R's,
John