[Savannah-hackers-public] Suspicious ‘451-You dont seem to have a reverse dns entry.’

[Tobias Geerinckx-Rice]

Hullo GNUs!

I noticed the following response in my mail logs:

--8<---------------cut here---------------start------------->8---
Nov 20 14:25:26 localhost smtpd[602]: 8be5d3679f9641dc mta 
delivery evpid=b7cb816f882ca1b8 from=<me@tobias.gr> 
to=<51512@debbugs.gnu.org> rcpt=<-> source="80.241.217.52" 
relay="209.51.188.43 (debbugs.gnu.org)" delay=3s result="Ok" 
stat="250 OK id=1moRJ1-0007Au-9p"
Nov 20 14:25:28 localhost smtpd[602]: 8be5d368064aaaa7 mta 
delivery evpid=b7cb816fe63e0547 from=<me@tobias.gr> 
to=<guix-patches@gnu.org> rcpt=<-> 
source="[2a02:c205:2020:6054::1]" relay="[2001:470:142:3::10] 
(eggs.gnu.org)" delay=5s result="TempFail" stat="451-You dont seem 
to have a reverse dns entry. Come back later. You aregreylisted 
for 20 minutes. See 
http://www.fsf.org/about/systems/greylistingfor more information."
Nov 20 15:25:30 localhost dovecot: imap-login: Disconnected: 
Connection closed (no auth attempts in 0 secs): user=<>, 
rip=2a01:4f8:251:53df:0:242:ac11:e, 
lip=2a02:c205:2020:6054::1:993, TLSv1.3 with cipher 
TLS_AES_256_GCM_SHA384 (256/256 bits)
Nov 20 15:25:31 localhost last message repeated 2 times
--8<---------------cut here---------------end--------------->8---

I might be missing an obvious, but that claim looks bogus from 
here:

--8<---------------cut here---------------start------------->8---
λ kdig -x 2a02:c205:2020:6054::1
;; ->>HEADER<<- opcode: QUERY; status: NOERROR; id: 61729
;; Flags: qr rd ra; QUERY: 1; ANSWER: 1; AUTHORITY: 0; ADDITIONAL: 
  0

;; QUESTION SECTION:
;; 
  1.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.4.5.0.6.0.2.0.2.5.0.2.c.2.0.a.2.ip6.arpa. 	IN 
  PTR

;; ANSWER SECTION:
1.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.4.5.0.6.0.2.0.2.5.0.2.c.2.0.a.2.ip6.arpa. 32400 
IN	PTR	tobias.gr.

;; Received 113 B
;; Time 2021-11-20 15:26:52 CET
;; From 127.0.0.1@53(UDP) in 82.4 ms

λ kdig tobias.gr aaaa
;; ->>HEADER<<- opcode: QUERY; status: NOERROR; id: 5449
;; Flags: qr rd ra; QUERY: 1; ANSWER: 1; AUTHORITY: 0; ADDITIONAL: 
  0

;; QUESTION SECTION:
;; tobias.gr.                   IN      AAAA

;; ANSWER SECTION:
tobias.gr.          	2454	IN	AAAA 
2a02:c205:2020:6054::1

;; Received 55 B
;; Time 2021-11-20 15:27:14 CET
;; From 127.0.0.1@53(UDP) in 0.1 ms
--8<---------------cut here---------------end--------------->8---

IPv4 seems equally in order, although the log mentions only IPv6.

My mail server is OpenSMTPd, and is configured to say HELO with 
the correct name:

--8<---------------cut here---------------start------------->8---
TX = "tobias.gr"
[…]
action send relay helo $TX
match tag out from auth  for any action send
--8<---------------cut here---------------end--------------->8---

I'd love to get rid of this >= 20-minute delay.  Please let me 
know if there's anything more I can do!

Kind regards,

T G-R

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