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  • Different IP addresses for receiving and sending mail

    Hi all,

    I'm configuring my internal network (after ISP changing) and I have some doubts..

    I have this particular configuration in my office

    Small Business Server 2003 as Domain Controller, Mail Server, etc installed on 192.168.20.1

    5 public ip addresses available (x.x.x.58 - x.x.x.62)

    x.x.x.58 assigned as external interface of our firewall (Fortigate 60)

    x.x.x.62 mapped to receive all our "ourdomain.it" traffic and (as virtual ip) maps INCOMING mail from port 25 to 192.168.20.1 (SBS2003) port 25
    (port 80 is mapped to another server, port 21 to another...and so on)

    I think that when we will SEND mail, SBS2003 will send to firewall (from internal to wan1 interface) and messages will exit from x.x.x.58 port 25

    Is it correct ? There is any problem with this configuration ?
    Is there any configuration I have to do on my DNS server ? (MX records...)

    Thanks



    Corrado

  • #2
    Re: Different IP addresses for receiving and sending mail

    Technically you shouldn't have a problem, MX records do not matter for outgoing mail (as long as you can resolve the recipients MX details obviously).

    Are you not using an SMTP relay then ? (i.e. Your ISP's ?).

    topper
    * Shamelessly mentioning "Don't forget to add reputation!"

    Comment


    • #3
      Re: Different IP addresses for receiving and sending mail

      Incoming mail traffic:
      You said "x.x.x.62 mapped to receive all our "ourdomain.it" traffic and (as virtual ip) maps INCOMING mail from port 25 to 192.168.20.1 (SBS2003) port 25" so there should be an MX record for ourdomain.it, something like
      ourdomain.it MX preference=10, mail exchanger= hostname.ourdomain.it
      where hostname.ourdomain.it IP address is x.x.x.62 and it is the hostname of your mail server

      Outgoing mail traffic:
      It is depends how the SMTP connector was configured. Exchange server can route outgoing emails directly (based on information received from DNS) or can use a smart host (mail gateway).

      For more details, here is a good link:
      http://www.msexchange.org/tutorials/...Connector.html

      Regards,
      Csaba
      Regards,
      Csaba Papp
      MCSA+messaging, MCSE, CCNA
      ...............................
      Remember to give credit where credit is due and leave reputation points where appropriate
      .................................

      Comment


      • #4
        Re: Different IP addresses for receiving and sending mail

        Thank you topper and netxt for your quick response

        I'm not using a SMTP relay, my Exchange routes outgoing mail directly

        I'm sorry netxt, I don't understand this part of your message

        " so there should be an MX record for ourdomain.it, something like
        ourdomain.it MX preference=10, mail exchanger= hostname.ourdomain.it
        where hostname.ourdomain.it IP address is x.x.x.62 and it is the hostname of your mail server"

        Where should this MX record be ? In my DNS server (SBS2003) or in my ISP DNS server ?

        Thank you

        Corrado

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        • #5
          Re: Different IP addresses for receiving and sending mail

          You will need to ensure that you have the PTR record setup for your x.x.x.58 address to show the mailserver or you will find that some mailservers (AOL in particular I found) will not accept mail from you.

          Other than that your setup will be about the same as mine, well except I have 4 mailservers using a different address in the zone file for the MX records as outbound connections.

          The pointer record will be controlled by your ISP.

          Comment


          • #6
            Re: Different IP addresses for receiving and sending mail

            Originally posted by MrMauy
            You will need to ensure that you have the PTR record setup for your x.x.x.58 address to show the mailserver or you will find that some mailservers (AOL in particular I found) will not accept mail from you.

            Other than that your setup will be about the same as mine, well except I have 4 mailservers using a different address in the zone file for the MX records as outbound connections.

            The pointer record will be controlled by your ISP.
            I knew there was something else I forgot !!

            Cheers MrMauy
            * Shamelessly mentioning "Don't forget to add reputation!"

            Comment


            • #7
              Re: Different IP addresses for receiving and sending mail

              Originally posted by MrMauy
              You will need to ensure that you have the PTR record setup for your x.x.x.58 address to show the mailserver or you will find that some mailservers (AOL in particular I found) will not accept mail from you.

              Other than that your setup will be about the same as mine, well except I have 4 mailservers using a different address in the zone file for the MX records as outbound connections.

              The pointer record will be controlled by your ISP.
              Thank you MrMauy
              I will surely have a "reverse DNS" of x.x.x.58 to be sure that every mail server will accept my messages

              Only one question more about this "MX record" story (I'm sorry but I don't understand it)

              Where will this MX record be ? In my DNS server or in my ISP ?
              Thank you

              Corrado

              Comment

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