451 4.4.0 DNS failed exchange 2010

I added a new exchange server and now mail start routing through that server. The email messages are stuck in that server with error 451 4.4.0 DNS query failed.

how do I configure the server not to route mails through this new server and just use the old server to rely email . Its a multirole server
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Will SzymkowskiSenior Solution ArchitectCommented:
I am assuming that you have installed another Exchange Server in the same AD Site? If this is correct Hub Transport Role will automatically work "out of the box" and be highly available without addtioinal configuration. This is by design.

Internal Mail should be routing fine however if you are getting this message when sending external eamil then just remove the new Exchange server from the Send Connector for Outgoing mail. This will force all of the Outgoing mail to go through the old Exchange sever and not the new one.

numanmalikAuthor Commented:
The new server is not mentioned anywhere in the send connector.  There are default receive connector created automatically when you install the server.
Md. MojahidCommented:
in the properties of the smarthostdeliveryconnector, Network tab,

try to check "Use the External DNS Lookup settings ont the transport server"

if already checked, try to specify dns servers explicitely


as a quick workaround for the time being, adding a line in the hosts table or using the ip addresses associated with the mimecast server in the connector should work
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numanmalikAuthor Commented:
I've requested that this question be deleted for the following reason:

Issue resolved
Will SzymkowskiSenior Solution ArchitectCommented:
Can you please elaborate on what the resolution was?

numanmalikAuthor Commented:
I added the server as authorized mail server to send email outbound in the receive connector. I think it was very basic which I probably forgot.

As soon you bring or install new hub server in a site. Exchange Hub transport Server will be automatically load balanced with in the Active Directory Site. Hub Transport Servers are load balanced in Round robin fashion with in the Site. If you want to Force Exchange Mailbox server to use specific Hub Server you need to make use of SUBMISSIONSERVEROVERRIDELIST

e.g  Set-MailboxServer -Id:MailboxServer1 -SubmissionServerOverrideList: htserver1,htserver2

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