Re: Help with sendmail ?

Path	csiph.com!fu-berlin.de!uni-berlin.de!individual.net!not-for-mail
From	"Carlos E.R." <robin_listas@es.invalid>
Newsgroups	comp.os.linux.misc
Subject	Re: Help with sendmail ?
Date	Sat, 31 Jan 2026 23:10:51 +0100
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On 2026-01-31 22:03, Lars Poulsen wrote:
> Please tell me if there is a better newsgroup that this for this topic.
> 
> I recently needed to reinstall my Linux workstation/server, which runs
> behind a Frontier Fiber Business Service with one static IP, with my
> own edge router behind it. So my mail server has both an internal
> IP address (linux-local.example.com 192.168.1.2) and a
> public IP address (linux.example.com w.x.y.z). There are also aliases
> defined in DNS:
>      www.example.com.  CNAME linux.example.com.
>      mail.example.com. CNAME linux.example.com.
> 
> Everything was working fine in my old setup, but after the new
> install, I can receive mail from the outside relayed from f.x. Gmail
> or my business email (which is hosted on Rackspace, but I cannot submit mail
> from the Windows machine on my LAN.  My IMAP (dovecot) server runs fine.
> I am puzzled.
> 
> Thunderbird on Windows reports that:
> | Sending of the message failed.
> | The sessage could not be sent because connecting to Outgoing server
> | (SMTP) linux-local.example.com failed. The server may be unavailable
> | or is refusing SMTP connections. Please verify that your Outgoing
> | server (SMTP) settings are correct and try again.
> |                                                      [OK]
> 

You should first look at the mail logs in the server at the same moment 
in time.

> I have tried many variations in my Thunderbird settings:
> * Specify host by IP address, internal name or public name
> * specify connection security None or STARTTLS
> * Port 25 or 587
> * Authentication None or Password, transmitted insecurely
> ... in every combination I can think of.
> 
> The failed connections do not show up in any of the logfiles
>    /var/log/messages
>    /var/log/maillog
>    /var/log/secure

Firewalls?

Wireshark?

> 
> I know from previous experience, that I should have STARTTLS
> enabled, because sendmail does not allow passwords to go on
> plain text TCP connections.
> 
> I think it must be a problem related to SSL, but sendmail.mc
> does nbot seem to mention any SSL configuration, and the RedHat
> sendmail deployment documention is very old and does not discuss
> where to specify the .pem files.
> 
> Where should I look next?
> 

use postfix. +1.

-- 
Cheers, Carlos.
ES🇪🇸, EU🇪🇺;

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Help with sendmail ? Lars Poulsen <lars@beagle-ears.com> - 2026-01-31 21:03 +0000
  Re: Help with sendmail ? Lawrence D’Oliveiro <ldo@nz.invalid> - 2026-01-31 21:22 +0000
    Re: Help with sendmail ? rbowman <bowman@montana.com> - 2026-02-01 03:02 +0000
      Re: Help with sendmail ? The Natural Philosopher <tnp@invalid.invalid> - 2026-02-01 10:58 +0000
        Re: Help with sendmail ? Lars Poulsen <lars@beagle-ears.com> - 2026-02-01 15:22 +0000
          Re: Help with sendmail ? Lawrence D’Oliveiro <ldo@nz.invalid> - 2026-02-01 20:12 +0000
          Re: Help with sendmail ? The Natural Philosopher <tnp@invalid.invalid> - 2026-02-01 20:43 +0000
          Re: Help with sendmail ? Marco Moock <mm@dorfdsl.de> - 2026-02-02 10:39 +0100
            Re: Help with sendmail ? Lawrence D’Oliveiro <ldo@nz.invalid> - 2026-02-02 21:29 +0000
  Re: Help with sendmail ? "Carlos E.R." <robin_listas@es.invalid> - 2026-01-31 23:10 +0100
    Re: Help with sendmail ? Resolved! Lars Poulsen <lars@beagle-ears.com> - 2026-02-01 01:03 +0000
      Re: Help with sendmail ? Resolved! Lawrence D’Oliveiro <ldo@nz.invalid> - 2026-02-01 02:27 +0000
      Re: Help with sendmail ? Resolved! c186282 <c186282@nnada.net> - 2026-02-01 00:34 -0500
  Re: Help with sendmail ? Marco Moock <mm@dorfdsl.de> - 2026-02-01 10:53 +0100

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