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  • rDNS

    Hi all

    Having a problem with rDNS, I think I know how to fix this but want to just double check.

    2 sites, one in UK and one in Germany.

    HQ is at UK and also holds the company's AntiSpam appliance.

    Users at Germany were getting lots of spam so they changed the MX record to point to the Spam Appliance at HQ which then forwards the clean mail to the Germany mailserver.

    Since this has happened users at Germany have been having outbound mail problems, NDR's received indicate rDNS or improper DNS config.

    When a reverse DNS lookup is performed for the Germany domain it points to the UK HQ Office IP. Outbound emails are sent direct from Germany.

    All that needs to happen is for me to call the ISP and get them to change the rDNS record to point to the Germany office IP address, correct?

    Thanks in advance.

    H

  • #2
    Re: rDNS

    If the email is going straight out, then the IP address needs to have a unique reverse DNS address. Ideally that means the FQDN on the server is also set to match.

    So you would need to have site2.example.com resolve to the the same IP address and have a matching reverse DNS.

    Simon.
    --
    Simon Butler
    Exchange MVP

    Blog: http://blog.sembee.co.uk/
    More Exchange Content: http://exchange.sembee.info/
    Exchange Resources List: http://exbpa.com/
    In the UK? Hire me: http://www.sembee.co.uk/

    Sembee is a registered trademark, used here with permission.

    Comment


    • #3
      Re: rDNS

      Thanks for the reply.

      I dont think I quite understand - could you please rephrase that for me please?

      HQ site in UK is has external domain name as company.co.uk, internal domain name is also company.co.uk

      Site in Germany has external domain name as company.de, but is on the same internal domain as HQ (different internal subnets)

      So at the moment the outbound emails from Germany are going straight out, on IP 217.243.x.x.

      The rDNS for mx1.company.de is resolving at the [strike]HQ Site IP Address.[/strike]

      EDIT: Sorry that was incorrect. There is currently NO rDNS for 217.243.x.x.

      ====

      So now I know I need to actually set rDNS up to start with - do I set 217.243.x.x to resolve to the ACTUAL server FQDN (mail.company.co.uk) or the MX record name? (mx1.company.de)

      ===

      Thanks
      Last edited by hongman; 8th July 2009, 12:52. Reason: Wrong Info

      Comment


      • #4
        Re: rDNS

        You are over complicating things.
        Internal domain has nothing to do with it.

        Simply decide what you to use as host name for the server, set it up in your public DNS. Then ask the ISP to set the same host name as the reverse DNS.

        Simon.
        --
        Simon Butler
        Exchange MVP

        Blog: http://blog.sembee.co.uk/
        More Exchange Content: http://exchange.sembee.info/
        Exchange Resources List: http://exbpa.com/
        In the UK? Hire me: http://www.sembee.co.uk/

        Sembee is a registered trademark, used here with permission.

        Comment


        • #5
          Re: rDNS

          Yeah I tend to over-complicate things

          Ok so

          The rDNS has been set to the mx record hostname : 217.243.x.x = mx1.company.de

          Now bear with me and sorry if this is stupid but from what you are saying, now I need to set up an A record pointing mx1.company.de to 217.243.x.x

          However, the mx1.company.de is already set to point to HQ's Spam Applicance.

          SO

          I need to now change the rDNS to servername.company.co.uk

          AND

          Set up an A record for servername.company.co.uk to point to 217.243.x.x

          Or am I hopelessly confused.

          Appreciate the patience.

          Comment


          • #6
            Re: rDNS

            Has nothing to do with the MX records.
            You could create an A record of server.example.com - as long as server.example.com resolves to the same IP address that has server.example.com set as its reverse DNS address, then you are fine.

            Simon.
            --
            Simon Butler
            Exchange MVP

            Blog: http://blog.sembee.co.uk/
            More Exchange Content: http://exchange.sembee.info/
            Exchange Resources List: http://exbpa.com/
            In the UK? Hire me: http://www.sembee.co.uk/

            Sembee is a registered trademark, used here with permission.

            Comment


            • #7
              Re: rDNS

              Gotit, I think,

              Thank you!

              Comment

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