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DNS server can find A records but not MX?

I have 12 DCs all running DNS.  My mail gateway is using one in particular for DNS and lately we've been getting a few of these

The following message to <xxxx@jpmchase.com> was undeliverable.
The reason for the problem:
5.4.7 - Delivery expired (message too old) 'DNS Soft Error looking up jpmchase.com (MX) while asking 192.168.75.x. Error was: ServFail'

so i tested looking up that MX record from that DC and it times out.  When I look it up from all the other DCs in the domain it finds it fine.  Also when I look up just the A record for JPMchase.com it finds it fine.  The only difference in configuration is that this DC has forwarders on (pointed to our ISPs DNS servers).  I took them off to see if that would make a difference but it still fails.  I've run dcdiag and netdiag and both come back clean.

any ideas what else could be going on?
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shanna1017
Asked:
shanna1017
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1 Solution
 
mcsweenSr. Network AdministratorCommented:
I would check to make sure the DNS forwarders are still correct.  Your DNS server shouldn't know about JPMChase.com so it will have to go to the ISP's DNS servers to get an answer.

You mentioned that your other DNS servers don't have forwarders setup, are you hosting the "." zone?  If so I suggest deleting it and handling all of those requests from your ISPs DNS.
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shanna1017Author Commented:
thanks for the quick reply.

i've used nslookup to lookup that address using those ISP DNS servers and it finds the MX record fine.  The other DNS servers are simply using root hints to find domains other than ours.  Is that what you're asking?
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mcsweenSr. Network AdministratorCommented:
OK, you are just using root hints.  I wanted to make sure you didn't have a forward lookup zone called "."  If you are you should delete it.

I know this seems silly, but have you tried restarting DNS services on the server or restarting the whole server?

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shanna1017Author Commented:
i've tried restarting the DNS service on that server but not the whole server since it's our main file/print server.  I will try that tonight
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shanna1017Author Commented:
actually i found a time when nobody had open files and quickly rebooted it.  still can't find the MX record.  

i don't get it?  what could be stopping it?  it's not in our domain so it should just use the forwarders to query the ISPs DNS servers right?  and those have already proven that they know about that record.  

strange
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glennbrown2Commented:
did this only start happening this afternoon?
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shanna1017Author Commented:
i think i actually fixed it by disabling Extension Mechanisms for DNS.  After I did that and restarted the service I was able to retrieve the MX record from that box.  either that or it was just coincidence.  Anybody have any explanation for why that would fix it?  The only reason I'm suspicious is because we only have 1 internet connection that all traffic from our WAN goes through so if that fixed the issue why would the other servers have been able to do it successfully with that feature turned on?
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ee_ai_constructCommented:
PAQ / Refund
ee ai construct, community support moderator
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