mail server 451 error

Posted on 2011-11-01
Last Modified: 2012-05-12
We are getting this error on an e-mail to domain:
20111031 113236       SMTP (a69d01910000722f) 451-Unable to
validate with the MX mailserver for
20111031 113236       SMTP (a69d01910000722f) 451
(tested with a fake bounce back)
Question by:nevyana2006
    LVL 22

    Accepted Solution

    Is the sat0tel address mentioned the sender? What it is saying is that the receiving mail server attempted to see if this was a valid address on your mail server. The test failed, so it won't accept your message.

    It could be your rDNS record isn't set up properly. You'll have to check with your service provider on that. Although I did find somebody else having the same problem with the host of (freeparking).

    Depending on how much email your organzation sends, you might think about the fact that if this is the only message that is failing, it might not be your server that is the problem.
    LVL 12

    Assisted Solution

    by:Gary Coltharp
    The recipient server is running code to verify sender identity and for some reason, either faulty self written code for verification or just the nature of your MX record, the test is failing.


    Author Comment

    its strange, as e-mail from a different domain is delivered. and on our domain we don't have another issue of the same nature. we are hosting the dns and there is a rDNS record.
    LVL 12

    Expert Comment

    by:Gary Coltharp
    Not that I believe the issues reported are causing this problem, you should really go to and run a report on your domain. You have several RFC violations in your config that you should attempt to resolve.


    Author Comment

    thank you both

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