On Sun, 13 Jul 2003, Walter Dnes wrote:
My proposal is for a NO_XMIT record in DNS. It effectively stands the
RMX proposal on its head. It would signify IP addresses that have no
business connecting to external MTAs. This would be very similar in
function to MAPS DUL(TM) and other lists of dynamic IP addresses. Here
is a sample implementation for discussion...
Some questions for discussion (I really like this proposal):
Given the nature of DNS, does the whole chain of clients and servers
need to be modified to support NO_XMIT, or just the servers? If everything
has to be updated, isn't that an argument for overloading and existing
record (such as MX, TXT, or SRV), at least during a transition period?
From the point of view of the sending ISP or autonomous system, what is
the advantage of supporting NO_XMIT, as compared to blocking outbound port
25 at the network edge? Is the problem router load, or philisophical?
Wouldn't that be both easier and more effective? Would the existence of a
formal standard for NO_XMIT make it more acceptable than blocking port 25?
Daniel Feenberg
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