How to Specify an External DNS Server That Is Used by the SMTP Virtual Server

To control the ports and IP addresses through which Exchange sends outbound mail, you must configure the SMTP virtual server. SMTP connectors configured on the virtual server inherit these settings.

Two of the SMTP virtual server properties relate directly to configuring Exchange to send Internet mail:

• The outbound TCP port    Verify that the outbound port is set to port 25, which is the default setting. For detailed instructions, see How to Verify an Outbound Port for Mail Delivery Is set to Port 25.

• **The use of an external DNS server   **To send Internet mail, the DNS server Exchange uses must be able to resolve external (Internet) names. Two common methods for configuring DNS to resolve external names include:

  • Configuring Exchange to point to an internal DNS server that uses forwarders to an external DNS server. This method is the easiest and most common approach, and it is outlined in the following procedure.

  • Configuring Exchange to point to an internal DNS server that does not have a forwarder to an external DNS server, and then configuring an external DNS server on the SMTP virtual server that is responsible for sending external mail.

Procedure

To specify an external DNS server that is used by the SMTP virtual server

1. In the Default SMTP Virtual Server Properties dialog box, on the Delivery tab, click Advanced.

2. In the Advanced Delivery dialog box, click Configure.

3. In the Configure dialog box (see the following figure), click Add to enter the IP address of an external DNS server. If you are using more than one external DNS server, use the Move Up and Move Down buttons to set the order of preference for the DNS servers.

   Configure dialog box for external DNS servers