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Reverse DNS (or how I didn't properly setup Exchange)

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  • Reverse DNS (or how I didn't properly setup Exchange)

    OK...here's a dumb question, I'm having a little bit of an issue with Reverse DNS and was hoping I could get some advice.

    First, a little background. Our Exchange 2K3 server is setup to send out all email thru SMTP (duh) and is located on our LAN only. All incoming mail first goes thru a Barracuda Spam Firewall that's sitting on our DMZ and then sent to Exchange. Our public MX record points to the Barracuda's public IP.

    Now, my issue seems to be related to Reverse DNS with certain hosts. When the mail process starts the receiving SMTP server resolves our Exchange server's IP back to public IP of our FW. And since that's not really where the message originated from it will drop the connection. This only happens for some hosts, the majority go thru without any issue.

    How do I properly set this up? Do I create a NAT for the Exchange box and register that outside public IP with DNS? Do I force all email traffic (including outbound) thru the Barracuda?

    As always, any help or advice would be appreciated.

  • #2
    Re: Reverse DNS (or how I didn't properly setup Exchange)

    Imho, easiest solution would be to configure the Baracuda as SMTP smarthost for outgoing emails also.
    At least thats what I would consider first.

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    • #3
      Re: Reverse DNS (or how I didn't properly setup Exchange)

      Originally posted by FischFra View Post
      Imho, easiest solution would be to configure the Baracuda as SMTP smarthost for outgoing emails also.
      At least thats what I would consider first.
      I'll give that a shot. Thanks!

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      • #4
        Re: Reverse DNS (or how I didn't properly setup Exchange)

        It's not going to hurt using the Barracuda as a smart host, but if Reverse DNS is the issue at the receiving end reverse DNS won't resolve it. You need to get your ISP to configure Reverse DNS.

        If you were to use your ISP's Smart Host then that would probably fix the issue, and many ISPs will suggest this to you rather than configuring Reverse DNS.
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