Re: firewall IP as Originating IP for emails

From: Steve Cowles (
Date: 09/09/04

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    Date: Thu, 09 Sep 2004 10:29:00 -0500
    To: General Red Hat Linux discussion list <>

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    On Stardate 6609.08, Mrs. Geeta Thanu said:

    | Hi Greshko,
    | Yah! what you are saying is correct I think.
    | I will just type the reason given by the domain which rejected our mail
    | ----------------------------------------------------
    | Permanent error involving remote host.
    | 554 5.7.1 The server sending your mail[] does not have a
    | reverse DNS entry.connection rejected.Please conatct your network ISP
    | provider.Default reject!
    | -------------------------------------------------
    | here the IP is our firewall IP
    | and the mail+web+DNS server IP is which is natted in the
    | firewall to a local IP.
    | Please help me to solve this problem.

    After re-reading the above, it looks like the OP may be asking about
    howto implement something like one-to-one NAT or a proxyarp type
    configuration at the firewall. This in addition to the DNS problems
    problems already mentioned.

    A good starting point at understanding one-to-one NAT can be found by

    There are many other helpful links at regarding this
    topic. Search for "proxyarp"

    - --
    Steve Cowles
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