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Exchange 2013, KEMP Load Balancer

Posted on 2015-02-24
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Last Modified: 2015-03-24
Dear experts, I'm running 2 X Exchange 2013 (all in one roles) in DAG mode. Both servers are behind a KEMP load balancer. The gateway of the Exchange servers are pointing to the KEMP LB.  I have a problem where mail to a certain domain experience this error "451 4.4.0 dns query failed". Under Exchange Settings in ECP and in DNS lookup under each server, I have used external DNS servers (including Gmail DNS server). I can run nslookup in each Exchange server to that domain with no problem. It can resolve the MX records. Also mail to external domains takes between 2 to 3 minutes to receive. The server is not heavily utilized. May I know what could be the problem?
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Question by:totallypatrick
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by:Simon Butler (Sembee)
Simon Butler (Sembee) earned 2000 total points
ID: 40630175
If you remove the external DNS records from within Exchange so it is using the domain controllers for DNS, what happens then? If you bypass the load balancers, what happens?

Simon.
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totallypatrick earned 0 total points
ID: 40677442
HI Sembre,
 
It's using the DNS server from my AD. I found the issue. Under the Send Connectors, I forgot to tick the Use external DNS lookup Settings on servers with transport roles.
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Author Closing Comment

by:totallypatrick
ID: 40684227
Found the solution to my problem
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