Dave,
On Sun, May 04, 2003 at 02:44:07PM -0700, Dave Crocker wrote:
if you find the rmx record, and then you know the posting is through an
authorized MTA.
if you do NOT find the rmx record, you do not know anything.
so, what is the real utility of the rmx record?
that's not how RMX works. That's how several different attempts to
whitelist authorized MTA's by giving them some kind of A record.
RMX works different.
When doing an RMX lookup for a given pair of sender domain name
and MTA IP address four different cases can occur:
* You get an RMX record and it does cover the sending MTAs IP address.
-> You know it is authorized
-> You know how many addresses are authorized,
e.g. 213.133.101.23/32 vs. 0/0 as a decision base
* You get an RMX record and it does not cover the IP address.
-> You know it is not authorized, at least not by RMX.
* You get an authoritative negative answer (No RMX)
-> You know that the domain owner refuses to publish
an RMX policy
* You don't get an answer (usual DNS reasons, timeout, routing
problem, server down...)
-> you do not know anything
So the utility of the rmx records are the first three of four
cases: They do provide you information needed to base your decision
about what to do with the email on.
regards
Hadmut
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