On wayne Friday, May 14, 2004 8:41 AM, Wayne [wayne(_at_)midwestcs(_dot_)com]
wrote
As a result, I believe that in practice, proposals that
describe the complete sets in a DNS cache friendly way will
have a slightly lower real DNS cost.
Agreed. Per-IP-based queries don't leverage DNS caching nearly as well.
Another point is that the domain is the administrative entity that's
most important here. Email policies make statemets about the behavior
of the domain so it makes sense to publish them in that way.