Problem sending emails to a particular domain name

Posted on 2008-11-17
Last Modified: 2013-11-15

Here is my problem : i have set up an exchange 2007 platform. My hub transport server is configured to use DNS to send emails directly through the Internet. For the moment, it works for every domain except one.

When I try to send emails to this exception, in the queue viewer I have an error message returned : "451 4.4.0 DNS Query failed".

But when I open a command prompt on my hub transport server, I type these lines :
server my_dns_server
set type = MX

The name resolution is done successfully...

Does anyone have an idea that could help me ?

Thanks in advance.

Question by:xelablub
    LVL 9

    Expert Comment

    i have seen dns have issues.
    try changing exchange to use dns servers, and  test it then.

    LVL 13

    Expert Comment

    Flush the cache and retry?

    Author Comment


    I tried with the public DNS server same error.

    I flushed the DNS cache: same error.

    I added a new send connector with a weight of 1 for the domain causing problem. This connector sends emails directly to the IP (to be sure there is no dns resolution): same error.......

    Good night.
    LVL 13

    Expert Comment

    I found this: (which may be relevant to you:)

    Have you tried forwarding DNS queries to an external DNS server and retry sending the message?


    Accepted Solution


    Thanks for the link but i have found a solution.

    On my hub transport send connector (i have no edge server for the moment), in the network tab I selected the "Use DNS MX records to route automatically" option.
    On the bottom of this screen there is a checkbox: "Use the external DNS lookup settings on the transport server". I checked it and now it works...

    But I still do not understand a thing: my internal DNS settings are the same as my external DNS settings which both point to my internal DNS server. So in fact, this checkbox has not changed many things... except that now it works...

    Thanks for the time you spent giving me ideas !

    LVL 13

    Expert Comment

    I believe that is what i suggested, forwarding queries to an external DNS server, anyway, glad to see that it is working, perhaps your DNS cache is corrupt, it happens all the time :)

    Author Comment

    The thing is that it was already sending emails through an external DNS. But my exchange server was using only the internal settings (my internal DNS server was relaying emails to an external DNS afterwards). The thing is that my external DNS settings also point to my internal DNS server !

    Anyway, if I was not using an external DNS at all, no emails could be sent, don't you think ? But my issue concerned only one domain. All others were working fine.


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