One final issue on the semantics issue. Do we include a DMP style of lookup
or not?
IE say something like:
LOOKUP(auth.example.com)
So if the source server is 10.0.0.1 the receiver looks up
1.0.0.10.auth.example.com
If we did this I think we need to have a positive value result test rather
than mere existence or not which is flaky if the admin of the zone changes.
I.e. test for a specific value (127.?.?.?) rather than existence or non
existence.
It is also possible to extend the qualified include idea to a scheme where
other parts of the header are tested. Here may lie the road to perdition, or
at least DoS potential. For example one can imagine a case where we have a
DMP style include that switches on the tested email address:
customer-service.example.com._marid.example.com MARID
"Record just for customer-service(_at_)example(_dot_)com"