How to Verify that MX Records Do Not Point to an Internal Domain

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When SMTP queries DNS, it always queries for MX records first. If an internal MX record exists and/or it is incorrectly configured, your internal mail delivery may not work.

Before You Begin

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

Procedure

To verify that MX records do not point to an internal domain

  1. At a command prompt, type nslookup, and then press ENTER.

  2. Type server <IP address>, where IP address is the IP address of your internal DNS server.

  3. Type set q=a, and then press ENTER.

  4. Type <fqdn>, where fqdn is the fully qualified name of your SMTP virtual server (and your Exchange server), and then press ENTER.

  5. Verify that the results that are returned match the IP address of the machine. On a multihomed computer, the IP address should match the IP address of the SMTP virtual server (except in the case of a single virtual server with an IP address of "All unassigned"). Your results should look similar to the following:

    set q=a
> server1.example.local
Name:    server1.example.local
Address:  192.168.1.10

    If the only result returned is the correct A record, internal name resolution should succeed. If there are no records, or if an MX record is returned and points to the wrong FQDN or IP address, other servers may be unable to send mail to this Exchange server.