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  • Internal mail server IP in header

    Hi guys,

    I have just received an NDR for an email I sent, which says:

    550 5.7.1 This system has been configured to reject your mail.
    An IP address (100.100.100.1 - our internal mail server's IP ) found in the message's 'Received:' headers is listed by the lookup site.

    Is there a way to hide our server's internal IP (both for security reasons and for preventing cases like this one?)

    thanks...

  • #2
    Re: Internal mail server IP in header

    Your internal IP address will be shown in the headers if the message is transferred between two SMTP servers inside. That behaviour cannot be changed unless you use a third party tool to strip the headers.

    However, from a security problem I personally think it is a null issue. If someone gets inside where they can use that information you have bigger problems to worry about.

    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: Internal mail server IP in header

      Originally posted by Sembee View Post
      Your internal IP address will be shown in the headers if the message is transferred between two SMTP servers inside...
      what do you mean?
      our exchange server uses an SMTP gateway which resides in DMZ as a "SmartHost", but the SMTP gateway is neither a member of the domain nor in the same network as the exchange server.

      Comment


      • #4
        Re: Internal mail server IP in header

        How do you think the message gets to the server in your DMZ?
        It is transferred by SMTP. The reference to "inside" is anything not on the internet.

        Therefore your email flow is

        Exchange, smart host, then out to the internet. The transfer between the Exchange server and the smart host will be in the headers. You cannot stop that as that is how SMTP is designed to work.

        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: Internal mail server IP in header

          I see.
          Had the guy who designed our company's network years ago followed the rules of private IP addressing, I wouldn't be in this mess right now...

          thanks Simon.

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