Call me crazy, but doesn't that use rDNS records?
no.
an MX receives a call from an IP
the IP sends
MAIL FROM:<[EMAIL PROTECTED]>
The MX looks up the forward zone for joshie.com (not the reverse zone) for the DMP TXT records (but no PTR records) to see if sending IP above is designated as the mailer for joshie.com.
If not, sender domain joshie.com is being forged, so MX hangs up.
Won't that freak out this group that can't deal with that?
not at all. DMP is optional
Am I wrong ?
yes
I was quickly skimming on page 6 and 7 and saw there are some RR records.
too quick, there are only TXT records. This does not even require the problematic reverse delegation and PTR to be present. It's all done in the forward domain, very simple, very elegant.
And, OPTIONAL, so it can be implmeneted when any domain owner gets around to.
If the MX looks up Joshie.com's DMP TXT records, and they don't exist, the MX concludes it can't verify the sending IP as DM for joshie.com. That does not mean to reject joshie.com.
eg, AOL, msn, yahoo could do DMP this immediately, like in 10 minutes, to help MXs every where kill forgery of those sender domains.
I've already done it for go2france.com:
# dig 75.210.73.212.in-addr._smtp-client.go2france.com. txt
; <<>> DiG 8.3 <<>> 75.210.73.212.in-addr._smtp-client.go2france.com. txt
;; res options: init recurs defnam dnsrch
;; got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 2
;; flags: qr aa rd ra; QUERY: 1, ANSWER: 1, AUTHORITY: 4, ADDITIONAL: 4
;; QUERY SECTION:
;; 75.210.73.212.in-addr._smtp-client.go2france.com, type = TXT, class = IN
;; ANSWER SECTION: 75.210.73.212.in-addr._smtp-client.go2france.com. 1D IN TXT "dmp=allow"
and :
# dig blah._smtp-client.go2france.com. any
; <<>> DiG 8.3 <<>> blah._smtp-client.go2france.com. any ;; res options: init recurs defnam dnsrch ;; got answer: ;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 2 ;; flags: qr aa rd ra; QUERY: 1, ANSWER: 1, AUTHORITY: 4, ADDITIONAL: 4 ;; QUERY SECTION: ;; blah._smtp-client.go2france.com, type = ANY, class = IN
;; ANSWER SECTION: blah._smtp-client.go2france.com. 1D IN TXT "dmp=deny"
Len
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