[anti-abuse-wg] Reverse DNS delegations

Fri Apr 5 14:41:01 CEST 2024

Have you asked them to setup PTR records?

We usually do it for our clients, so I’ve no idea how others handle it

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From: anti-abuse-wg <anti-abuse-wg-bounces at ripe.net> on behalf of Alessandro Vesely <vesely at tana.it>
Date: Friday, 5 April 2024 at 13:01
To: anti-abuse-wg <anti-abuse-wg at ripe.net>
Subject: [anti-abuse-wg] Reverse DNS delegations
[EXTERNAL EMAIL] Please use caution when opening attachments from unrecognised sources.

Hi all,

what's the policy for reverse delegation?  My provider assigned me a 2a02:29e1:500:6c00::/56.  Great.  However they didn't delegate reverse DNS.  Indeed, their own 2a02:29e1::/32 has no delegations:

; <<>> DiG 9.18.24-1-Debian <<>> 1.e.9.2.2.0.a.2.ip6.arpa ns
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NXDOMAIN, id: 19800
;; flags: qr rd ra ad; QUERY: 1, ANSWER: 0, AUTHORITY: 1, ADDITIONAL: 1

;; OPT PSEUDOSECTION:
; EDNS: version: 0, flags:; udp: 1232
; COOKIE: cad8ae482b0e559c01000000660fe49763aa815e05fda159 (good)
;; QUESTION SECTION:
;1.e.9.2.2.0.a.2.ip6.arpa.      IN      NS

;; AUTHORITY SECTION:
0.a.2.ip6.arpa.         3600    IN      SOA     pri.authdns.ripe.net. dns.ripe.net. 1712314758 3600 600 864000 3600

Now there are mail servers which reject mail if they don't find a matching PTR:

  <<< 554 resimta-c2p-559421.sys.comcast.net resimta-c2p-559421.sys.comcast.net 2a02:29e1:500:6c00::4 Comcast requires that all mail servers must have a PTR record with a valid Reverse DNS entry. Currently your mail server does not fill that requirement. For more information, refer to: https://postmaster.comcast.net/smtp-error-codes.php#554

Why isn't it possible to gain a delegation by proving number assignment?

Best
Ale
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