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External connection to Postfix problem

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  • Gary Brinker
    Because of a hardware failure on an old installation of a postfix gateway I took the opportunity to install an up to date version on an Ubuntu server. I am not
    Message 1 of 5 , Jun 20, 2013
       Because of a hardware failure on an old installation of a postfix gateway I took the opportunity to install an up to date version on an Ubuntu server. I am not too far into the configuration but am having a basic problem with accessing it from external sites. I think I can eliminate the usual DNS and router configurations as it did work correctly with the old system.
      The issue is that I can telnet into it internally with no problem but cannot reach it externally. I hooked up wireshark and if I'm interpreting it correctly I do find the initial SYN come in but no connection is established. My reading suggests that I may have an ownership or permissions problem, but I'm not finding success in isolating the issue.
      Can anyone point out specifically what I should be looking at to diagnose and correct this so I can get on to the meat of the configuration.
      Thanks for any suggestions.
      Gary
    • Wietse Venema
      ... Report the output from telnet postfix-ip-address 25 from a different machine on your local network. Wietse
      Message 2 of 5 , Jun 20, 2013
        Gary Brinker:
        > The issue is that I can telnet into it internally with no problem
        > but cannot reach it externally. I hooked up wireshark and if I'm
        > interpreting it correctly I do find the initial SYN come in but
        > no connection is established.

        Report the output from "telnet postfix-ip-address 25" from a
        different machine on your local network.

        Wietse
      • Scott Kitterman
        ... I think it s stunningly unlikely that you are having an issue related to upstream Postfix issues. I would recommend using an Ubuntu server specific venue
        Message 3 of 5 , Jun 20, 2013
          On Thursday, June 20, 2013 10:19:25 AM Gary Brinker wrote:
          > Because of a hardware failure on an old installation of a postfix gateway I
          > took the opportunity to install an up to date version on an Ubuntu server.
          > I am not too far into the configuration but am having a basic problem with
          > accessing it from external sites. I think I can eliminate the usual DNS and
          > router configurations as it did work correctly with the old system. The
          > issue is that I can telnet into it internally with no problem but cannot
          > reach it externally. I hooked up wireshark and if I'm interpreting it
          > correctly I do find the initial SYN come in but no connection is
          > established. My reading suggests that I may have an ownership or
          > permissions problem, but I'm not finding success in isolating the issue.
          > Can anyone point out specifically what I should be looking at to diagnose
          > and correct this so I can get on to the meat of the configuration. Thanks
          > for any suggestions.

          I think it's stunningly unlikely that you are having an issue related to
          upstream Postfix issues. I would recommend using an Ubuntu server specific
          venue to try and fix the problem. One would be:

          https://lists.ubuntu.com/mailman/listinfo/ubuntu-server

          Scott K
        • Gary Brinker
          ... The output from the internal address is the 250 greeting banner and using the external IP is could not open connection : connection failed Gary
          Message 4 of 5 , Jun 20, 2013

             

            > Report the output from "telnet postfix-ip-address 25" from a
            > different machine on your local network.
            >
            > Wietse
             

            The output from the internal address is the 250 greeting banner and using the external IP is
            could not open connection : connection failed
             
            Gary
          • Wietse Venema
            ... This confirms that Postfix accepts network connections, and that the problem is outside of Postfix. It could be any of: - Incorrect default route
            Message 5 of 5 , Jun 20, 2013
              Wietse:
              > Report the output from "telnet postfix-ip-address 25" from a
              > different machine on your local network.

              Gary Brinker:
              > The output from the internal address is the 250 greeting banner
              > and using the external IP is could not open connection : connection
              > failed Gary

              This confirms that Postfix accepts network connections, and
              that the problem is outside of Postfix.

              It could be any of:
              - Incorrect default route configured on the Postfix host
              - Incorrect firewall configuration on the Postfix host
              - Incorrect LAN router configuration (NAT/forwarding)
              - Conflict with ISP-side configuration
              - ....

              This is a matter of systematic trouble shooting, or random experiments
              and dumb luck.

              Wietse
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