What is this "IP+domain" thing? That is two queries, right? One for
the _smtp-client.$FQDN and one for the $REV-ADDRESS....$FQDN.
It's two queries, but you usually need only to make one of them.
As the FSV draft says, it panders to both camps. If you have the kind
of SMTP server where you want to slurp up the data once and remember
it for subsequent sessions, you fetch the TXT record that has all of
the info for the domain, parse it, and remember it. If you have the
kind of server that starts a new process for each session, you check
the IP+domain record to see if the IP you're talking to is listed.
DMP and FSV share a common problem of no easy way to tell the
difference between an IP+domain record that doesn't exist because the
IP isn't valid and one that doesn't exist because the domain publishes
no LMAP data at all. In that case, if you care, you have to go back
and check to see if the base record exists, so that'd be a second
query.
Regards,
John Levine, johnl(_at_)taugh(_dot_)com, Taughannock Networks, Trumansburg NY
http://www.taugh.com