DNS client failing to query a particular domain only.

[Manjunath H N]

Hi, 
A client of our company is not able to query any DNS records for our
domain, I tried troubleshooting at my end & confirmed that there was no
error at our end. 

I somehow managed to get access to one of the machines in their network
& when I try to query for any DNS RR or simple name lookup for our
domain, it gives DNS Timed out error, so I thought it could be a problem
with their DNS & I did a lookup using other name servers on the same
client machine, but still getting the same DNS Timed out errors. I also
tried increasing the querying time to 10 seconds, but that did not help
much either. 

Also he claims that our records don't exist on Root Servers, which is
not true. 

And because of this they are not able to send mails to my domain, as it
gives DNS Query failure. 

I am not sure what DNS they are using, so don't know whether it is
patched correctly or not. 

Could this be because of Cache poisoning ?? I am going to have a call
with the team today & try to analyze what else could be the problem. 

TIA 
Manjunath