Topic Last Modified: 2005-11-18

The Microsoft® Exchange Server Analyzer Tool queries the Active Directory® directory service to determine the value for the msExchSMTPExternalDNSServers attribute in the protocolCfgSMTPServer class for the Exchange Server object. The protocolCfgSMTPServer class contains the settings for an SMTP virtual server. If the msExchSMTPExternalDNSServers attribute is set, the SMTP virtual server uses an external DNS server. If the Exchange Server Analyzer determines that the msExchSMTPExternalDNSServers attribute is set, a warning is displayed.

If you configure your SMTP virtual server to use an external DNS server, you may experience performance problems. Therefore, this configuration is not recommended.

To change the external DNS setting on an SMTP virtual server
  1. In Exchange System Manager, expand Servers, expand <your inbound Exchange server>, expand Protocols, and then expand SMTP.

  2. Right-click your SMTP virtual server, and then click Properties.

  3. Click the Delivery tab, and then click Advanced.

  4. Click Configure to configure external DNS servers.

  5. To add an external DNS server, click Add, type the IP address of the external DNS server in the Add dialog box, and then click OK.

  6. To remove an external DNS server, select an IP address, and then click Remove.

  7. Click OK.

For more information about configuring DNS in your Exchange Server 2003 organization, see "Configuring DNS" in the Exchange Server 2003 Transport and Routing Guide (

For more information about configuring SMTP connectors to link to Internet domains in Exchange, see the Microsoft Knowledge Base article 319426 "How To Configure the SMTP Connector to Link to Internet Domains in Exchange" (