On Thu, 18 Jun 2009, Rich Kulawiec wrote:
On Tue, Jun 16, 2009 at 11:36:37PM -0400, Bill Cole wrote:
That said, I think that adding DNS records that map specific network
addresses to their legitimate behaviors in a generalized model would be a
positive advance.
+1. For instance, I (semi-seriously, semi-facetiously) proposed "XM"
records some years ago, whose value would be 0 or 1: hosts with 1 send
SMTP traffic, hosts with 0 don't. Thus every MX's behavior could be
to reject all port 25 SMTP connections from hosts with XM=0.
There a lot of problems with this idea, and if memory serves, both
Dave Crocker and John Levine pointed them out at the time. But I think
Are there problems that would extend beyond the problems of traders in
improper material who don't want their material sitting in queues on the
ISP MTA? This is usually dressed up as "The FBI is after me for my
advanced political views" or "My ISP is an evil monopolist", but are there
problems for other users of email?
I would also add that the "end to end" principle, however much it applies
to voluntary associations between endpoints, can hardly be applied to the
SMTP protocol, where complete strangers are expected to interact. Sites
will always be cautious of strangers, and asking that SMTP senders be
vouched for by their DNS providor is a very small concession indeed.
Furthermore, the "endpoint" in the "end-to-end" principle is a host, not
a user, so it is perfectly within the principle to is a host IP address as
a discrimination device.
Daniel Feenberg
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