Default Exchange 2007 DNS query
Hello, I am a Tier 2 support rep. for Microsoft's Forefront Online Protection for Exchange. I do not have extensive Exchange support experience, and I came here in the hopes of finding an answer to what I would think would be an easy question for you Exchange pros. While I understand there is no default send connector in Exch 2007, what would the default DNS query order of events be? What I mean is, for an external email, would Exch query the quad A record first or the A record? From what I understand, Exchange 2010 is going to query for the IPv6 Quad A record before an IPv4 A record. Does the same hold true for 2007? If so, does this behavior only apply to a certain SP?
February 27th, 2011 8:22pm

As a follow up, I ran through all the basic searches I could on this issue and couldn't find an answer. Is this covered somewhere I'm not looking? Thanks in advance.
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February 27th, 2011 8:24pm

The DNS query is at the OS DNS client stack and is Exchange agnostic. For example if a client is not configured for IPV6 it will not query for IPV6 records. If a client is configured for both IPV6 and IPV4, IPV6 is preferred. This is handled by the client DNS resolver. If IPV6 record is returned but the target server is not configured for IPV6 it will time out and fall back to IPV4. At this point Exactly handles the fall back mechanism. The details of the fallback mechanism works within Exchange I'm not sure, likely "code"James Chong MCITP | EA | EMA; MCSE | M+, S+ Security+, Project+, ITIL msexchangetips.blogspot.com
February 27th, 2011 9:03pm

Hi James has given clear explanation. Most of network only supports IPv4.So it will cause many problems. This article is about how to disable IPv6. Maybe it is helpful to you. http://support.microsoft.com/kb/929852
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February 28th, 2011 9:54pm

Hi Do you have anything to update now ?
March 3rd, 2011 3:13am

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