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rdns resolving not working for IPv4

From Marco Moock <mm@dorfdsl.de>
Newsgroups comp.mail.sendmail
Subject rdns resolving not working for IPv4
Date 2026-04-06 15:27 +0200
Organization A noiseless patient Spider
Message-ID <10r0cbo$240cu$4@dont-email.me> (permalink)

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Hallo!

I am using sendmail 8.18.1 on Debian 13.
systemd-resolve is running as a local stub resolver and working.


u@pi-dach:~$ dig -x 95.216.221.164 @127.0.0.53 +short
smtp.eternal-september.org.
u@pi-dach:~$ dig a smtp.eternal-september.org. +short
95.216.221.164
u@pi-dach:~$ 

u@pi-dach:~$ getent hosts 95.216.221.164
95.216.221.164  smtp.eternal-september.org
u@pi-dach:~$ 



That happens for multiple servers, so it is not an issue of this
specific sending server.

It does work for IPv6 sending servers, but not for IPv4.

How can I further diagnose this?

I've tried -bt and saw the proper queries in the tcpdump.
Although, it does not display the results in the -bt mode (maybe I use
it wrong).

-- 
kind regards
Marco

Send unsolicited bulk mail to 1775481321muell@stinkedores.dorfdsl.de

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Thread

rdns resolving not working for IPv4 Marco Moock <mm@dorfdsl.de> - 2026-04-06 15:27 +0200
  Re: rdns resolving not working for IPv4 Claus Aßmann <INVALID_NO_CC_REMOVE_IF_YOU_DO_NOT_POST_ml+sendmail(-no-copies-please)@esmtp.org> - 2026-04-06 12:29 -0400
    Re: rdns resolving not working for IPv4 Marco Moock <mm@dorfdsl.de> - 2026-04-06 20:26 +0200
      Re: rdns resolving not working for IPv4 Claus Aßmann <INVALID_NO_CC_REMOVE_IF_YOU_DO_NOT_POST_ml+sendmail(-no-copies-please)@esmtp.org> - 2026-04-06 15:18 -0400
        Re: rdns resolving not working for IPv4 Claus Aßmann <INVALID_NO_CC_REMOVE_IF_YOU_DO_NOT_POST_ml+sendmail(-no-copies-please)@esmtp.org> - 2026-04-06 16:13 -0400
        Re: rdns resolving not working for IPv4 Marco Moock <mm@dorfdsl.de> - 2026-04-07 15:32 +0200
          Re: rdns resolving not working for IPv4 Claus Aßmann <INVALID_NO_CC_REMOVE_IF_YOU_DO_NOT_POST_ml+sendmail(-no-copies-please)@esmtp.org> - 2026-04-07 14:55 -0400
            Re: rdns resolving not working for IPv4 Marco Moock <mm@dorfdsl.de> - 2026-04-08 20:44 +0200
              Re: rdns resolving not working for IPv4 Marco Moock <mm@dorfdsl.de> - 2026-04-08 20:46 +0200
                Re: rdns resolving not working for IPv4 Lew Pitcher <lew.pitcher@digitalfreehold.ca> - 2026-04-08 21:23 +0000
                Re: rdns resolving not working for IPv4 Marco Moock <mm@dorfdsl.de> - 2026-04-09 19:36 +0200
                Re: rdns resolving not working for IPv4 Lew Pitcher <lew.pitcher@digitalfreehold.ca> - 2026-04-09 18:23 +0000
                Re: rdns resolving not working for IPv4 Marco Moock <mm@dorfdsl.de> - 2026-04-09 20:30 +0200
                Re: rdns resolving not working for IPv4 Claus Aßmann <INVALID_NO_CC_REMOVE_IF_YOU_DO_NOT_POST_ml+sendmail(-no-copies-please)@esmtp.org> - 2026-04-09 02:42 -0400
                Re: rdns resolving not working for IPv4 Marco Moock <mm@dorfdsl.de> - 2026-04-09 20:02 +0200
                Re: rdns resolving not working for IPv4 Bjørn Mork <bjorn@mork.no> - 2026-04-09 20:48 +0200
                Re: rdns resolving not working for IPv4 Marco Moock <mm@dorfdsl.de> - 2026-04-09 21:16 +0200
                Re: rdns resolving not working for IPv4 Claus Aßmann <INVALID_NO_CC_REMOVE_IF_YOU_DO_NOT_POST_ml+sendmail(-no-copies-please)@esmtp.org> - 2026-04-09 15:07 -0400
              Re: rdns resolving not working for IPv4 Claus Aßmann <INVALID_NO_CC_REMOVE_IF_YOU_DO_NOT_POST_ml+sendmail(-no-copies-please)@esmtp.org> - 2026-04-09 13:48 -0400
                Re: rdns resolving not working for IPv4 Marco Moock <mm@dorfdsl.de> - 2026-04-09 20:15 +0200
                Re: rdns resolving not working for IPv4 Claus Aßmann <INVALID_NO_CC_REMOVE_IF_YOU_DO_NOT_POST_ml+sendmail(-no-copies-please)@esmtp.org> - 2026-04-09 14:23 -0400
                Re: rdns resolving not working for IPv4 Marco Moock <mm@dorfdsl.de> - 2026-04-09 20:38 +0200

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