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How to Use the DNS Resolver to Verify DNS Configuration


Topic Last Modified: 2006-10-12

For Exchange Server to send Internet mail, the DNS servers that Exchange Server uses for your domain must be able to resolve external domain names. To verify that your DNS servers can resolve external domain names, use the DNS Resolver tool (Dnsdiag.exe) if you are running Exchange Server 2003 on Windows Server 2003.

Before you perform the procedure in this topic, read Verifying DNS Design and Configuration.

The DNS Resolver tool is included with the Microsoft Windows Server 2003 Resource Kit Tools. For more information about how to install and use the DNS Resolver tool, see Microsoft Windows Server 2003 Resource Kit Tools.

  1. On your Exchange Server, copy dnsdiag.exe to the path C:\WINNT\system32\inetsrv directory, where C is the drive to which Windows Server is installed.

  2. Open a command prompt and navigate to the inetsrv directory.

  3. At the command prompt, type the following:

    dnsdiag contoso.com -v 1

    where contoso.com is an external domain and 1 is the instance number of the SMTP virtual server that you want to use.

    The mail exchanger (MX) resource record for the domain that you entered should be displayed. If the MX record is not displayed, DNS is not configured to resolve external domain names.

The following example shows how the DNS server for example.com resolves the IP address of the external domain contoso.com:

Created Async Query:


        QNAME = contoso.com

        Type = MX (0xf)

        Flags =  UDP default, TCP on truncation (0x0)

        Protocol = UDP

        DNS Servers: (DNS cache will not be used)

Connected to DNS over UDP/IP.

Received DNS Response:


        Error: 0

        Description: Success

        These records were received:

        contoso.com    MX    10    mail.contoso.com

        mail.contoso.com    A


Processing MX/A records in reply.

Sorting MX records by priority.


Target hostnames and IP addresses


HostName: "mail.contoso.com"

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