DNS Resolution Issue

We recently created a new domain called “testusa.com”.  We are running one Windows Server 2008R2 DC which is acting as the DNS server.  Our current external mail provider has us use the address “mail.testusa.com” for our web-based email and for configuring Outlook settings.  The matching of the domain and the mail provider’s given address was unintentional.  If I use the Domain Controller’s internal IP as the primary DNS server for our workstations, they fail to navigate to the mail provider.  If I manually set the workstations to only use external DNS server’s, they correctly navigate to the email provider.  How can I have the workstation correctly use the DC as their primary DNS server, but also have them navigate to the email provider?  Any help would be great appreciated!
zargf8nsAsked:
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TunerMLConnect With a Mentor Systems EngineerCommented:
Host A record in your internal DNS server for mail.testusa.com pointing to the correct external ip should work, if not just use a MX record.
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ajbarronCommented:
You can effectivly get through this in two different ways. You can add a record to your internal DNS server that resolves mail.testusa.com to the correct IP address or you can make your internal DNS forward unresolved queries to the external DNS.

To set up a forwarder:

Open DNS Manager
In the console tree, click the applicable DNS server
On the Action menu, click Properties
On the Forwarders tab, under DNS domain, click a domain name
Under Selected domain's forwarder IP address list, type the IP address of the external DNS server, and then click Add


You might need to flush the DNS cache on the clients if you want to see the results straight away using ipconfig \flushdns


Hope this helps,
Anthony
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zargf8nsAuthor Commented:
Thanks for the suggestions.  If I want to add a record to our internal DNS server, would it be under forward lookup zones?  My brief understanding of Host A records indicates they are for internal IP addresses.  Can I simply add a new Host A with name "mail" and the matching external IP address?

Thanks!
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FrabbleConnect With a Mentor Commented:
A records can have any IP address you wish, so having an A record for "mail" with the external address will work. However it is better done with name server delegation.

For the domain, you select Action to be New Delegation. The name is that of the host "mail" and the name server entries are that of the external DNS servers. Any queries for mail.testusa.com to your name servers will be referred to the external ones.
It also means any changes to the external records do not involve any changes by you.
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footechConnect With a Mentor Commented:
Forward Lookup zones can include records with both internal and external IPs, it doesn't matter.  You can just create the A record for "mail" with the extenal IP.
In this case, setting up a forwarder would not help you at all since your DNS is authoritative for the testusa.com domain.
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HaslerctCommented:
Don't make thing complicated... Just create a new A record and point to external IP. Full Stop!  

Cheers....
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zargf8nsAuthor Commented:
I created a A record pointing to the external IP and now the mail is moving.  If I find the external IP changing, I might have to attempt a delegation.  Thanks!!
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