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| From | Marco Moock <mm@dorfdsl.de> |
|---|---|
| Newsgroups | comp.mail.sendmail |
| Subject | Re: rdns resolving not working for IPv4 |
| Date | 2026-04-07 15:32 +0200 |
| Organization | A noiseless patient Spider |
| Message-ID | <10r3113$2rm5f$1@dont-email.me> (permalink) |
| References | <10r0cbo$240cu$4@dont-email.me> <10r0n20$kvr$1@news.misty.com> <10r0ttg$25too$1@dont-email.me> <10r10tf$fr$1@news.misty.com> |
On 06.04.2026 15:18 Uhr Claus Aßmann wrote: > Marco Moock wrote: > > > Messages are being rejected because sendmail thinks the PTR doesn't > > match the hostname, but DNS works properly. > > Maybe DNS works properly, but whatever your "systemd" crap > is doing is most likely broken. > > Example; > If /etc/nsswitch.conf uses myhostname for the hosts service and it > is listed after dns, then a temporary dns failure will result in a > permanent error - which obviously is completely bogus and something > systemd introduced based on a poor decision by some developer(s) hosts: files myhostname resolve [!UNAVAIL=return] dns That is the default when installing Debian. > Moreover, why (and how) do you reject message based on this? Certain spammer-controlled systems have improper rdns - normal mail relays have set PTR records properly. I used FEATURE(`require_rdns')dnl in the past for that. > > > /dnslookup smtp.eternal-september.org > > Why do you only provide part of the debugging? > What is "dnslookup"? (a map but what's the K line in the cf file)? > What is the output of the command? u@pi-dach:~$ echo '/dnslookup smtp.eternal-september.org AAAA' | sudo sendmail -bt -d8.64 _res.options = 41012c3, HasWildcardMX = 0 ADDRESS TEST MODE (ruleset 3 NOT automatically invoked) Enter <ruleset> <address> > dns_lookup_int(smtp.eternal-september.org, 1, AAAA, 0) dns_lookup_int(smtp.eternal-september.org, 1, AAAA, 0)=83 parse_dns_reply: ac=1, ad=0 dns2he: ad=0 > u@pi-dach:~$ echo '/dnslookup smtp.eternal-september.org A' | sudo > sendmail -bt -d8.64 _res.options = 41012c3, HasWildcardMX = 0 ADDRESS TEST MODE (ruleset 3 NOT automatically invoked) Enter <ruleset> <address> > dns_lookup_int(smtp.eternal-september.org, 1, A, 0) dns_lookup_int(smtp.eternal-september.org, 1, A, 0)=71 parse_dns_reply: ac=1, ad=0 parse_dns_reply: IPv4=95.216.221.164 dns2he: ad=0 > u@pi-dach:~$ > u@pi-dach:~$ echo '/dnslookup 164.221.216.95.in-addr.arpa PTR ' | sudo sendmail -bt -d8.64 _res.options = 41012c3, HasWildcardMX = 0 ADDRESS TEST MODE (ruleset 3 NOT automatically invoked) Enter <ruleset> <address> > dns_lookup_int(164.221.216.95.in-addr.arpa, 1, PTR, 0) dns_lookup_int(164.221.216.95.in-addr.arpa, 1, PTR, 0)=96 parse_dns_reply: ac=1, ad=0 parse_dns_reply: type=PTR, host=smtp.eternal-september.org dns2he: ad=0 > u@pi-dach:~$ > What is used to show that the IP does not resolve properly? STARTTLS=server, relay=[95.216.221.164] Normally, the host name is listed there if DNS lookup is working. -- kind regards Marco Send spam to 1775481487muell@stinkedores.dorfdsl.de
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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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