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Is it possible to use same domain name in two mail servers?

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  • Is it possible to use same domain name in two mail servers?

    Hi. I have my mail hosted by our ISP via POP3. I have a domain name of company.com. I have an email which is [email protected]. Now I have exchange 2003 hosted locally in our site to be used also as an internet mail. I want to create a new email which is [email protected] in exchange 2003. I want to retain the POP3 from our ISP for the meantime until the exchange 2003 is fully functional so that I can transfer all other email from the ISP.

    Is the scenerio above possible? I have read that it is possible to have two MX records for other purposes but I'm not sure of this one. Do you think it is possible to create two emails in two different mail server that is fully functional that can send and receive internet emails?

    Please help. Thank you.

  • #2
    Re: Is it possible to use same domain name in two mail servers?

    I hope i understaned your question correctly.
    For short:
    Yes, you can BUT....
    You can set a second mx record with a higher or lower connection valliue.
    For example:
    Your ISP has MX= 13.13.13.1 10
    Internal MX = 14.14.14.14 20
    If the MX of the ISP is unavailable than mail wil be forwarded to the MX record with a higher connection prefix, in this case 14.14.14.14 20.
    As long as the MX with the lowest prefix is available, mail will always pass through that MX.

    BUT....:
    You have to make sure that a mailbox for the user is available on your server.
    Because PTR's are missing some mail could not be recieved, when the sending server does an reverse lookup.
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    • #3
      Re: Is it possible to use same domain name in two mail servers?

      The MX record method outlined above will not work.
      You cannot control where email goes via MX records. If you have two servers in the MX records then both servers will receive email. The one with the higher priority level will get more spam. There is no way to control which server gets email and which does not.
      The priority level is theory only, in practise it doesn't work.

      While you can have email addresses on both servers, there will be no way of getting email down from the ISP to the Exchange server unless you are using SBS and can configure the POP3 connector.

      Sending email will not be a problem.

      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.

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      • #4
        Re: Is it possible to use same domain name in two mail servers?

        Does it mean that if the [email protected] in server A (from ISP via POP3) will send an email to [email protected] in server B (from exchange server) the [email protected] (from exchange server) will not be able to receive the mail?

        Could you give me some suggestions on how to resolve this kind of scenario before we transfer all of email from ISP to exchange? I have read that from MX record pointing it will take maximum of three days for it to work? Is this true? If so, we can't afford to lose emails.
        Last edited by heavenknows; 12th February 2008, 07:34.

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        • #5
          Re: Is it possible to use same domain name in two mail servers?

          Most ISPs networks are setup to presume that they are responsible for ALL email for the domain. Therefore if you send email to a user account on the Exchange server, the ISPs network will not know that the Exchange server exists and will simply NDR the email back to the sender as user unknown.

          Full DNS propagation takes at least 48 hours to be safe. You can reduce that using dynamic DNS tricks.

          However what I do for this type of move is have both systems running.

          The Exchange server has all email addresses in place.
          All clients are changed so that they have both Exchange (as primary) and the old POP3 account in their Outlook. Import all the email in.
          Then change the MX records. Email comes in to either the old or the new server and the client receives it. Eventually email will stop coming in to the ISPs servers and you can remove the configuration.

          No email is lost, all that happens is that it could be delivered to one or other of the servers. You have no way of knowing.

          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


          • #6
            Re: Is it possible to use same domain name in two mail servers?

            Just clarify me if im getting this correct, since i already have an email account of [email protected] in ISP mail, I could also configure the [email protected] in my exchange? Now sending and receiving mail to other email account in ISP mail won't have any issue?

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            • #7
              Re: Is it possible to use same domain name in two mail servers?

              If you create an account on the Exchange server that matches an account with the ISP, you will be able to send email ok. However replies will not come to the Exchange server, they will go to the ISP.

              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


              • #8
                Re: Is it possible to use same domain name in two mail servers?

                In order the mails to come to exchange I need to switch the MX records for the exchange to receive mails? If I will exchange the MX records in which my primary is the exchange and the ISP is the secondary, will the POP3 account from ISP will still able to receive mails?

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                • #9
                  Re: Is it possible to use same domain name in two mail servers?

                  You will need to add the Exchange server to the MX records for email to come in to Exchange. However some email will continue to be delivered to the ISPs servers instead of yours. The only way that you can stop that is to remove the ISP from the MX records completely.
                  As long as the ISP doesn't change anything then email delivery to the ISPs servers will continue.

                  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


                  • #10
                    Re: Is it possible to use same domain name in two mail servers?

                    Ok, thank you so much for your help.

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