Some of your SMTP e-mail messages may remain in your outgoing mail queues with a status of 'Unable to bind to the destination server in DNS' in Exchange 2000 Server and in Exchange Server 2003

In Microsoft Exchange 2000 Server and in Microsoft Exchange Server 2003, some of your SMTP e-mail messages may remain in your outgoing mail queues in Exchange System Manager. Additionally, if you view the properties of a message in Queue Viewer in Exchange 2000 Server, the Details tab shows the following status for the message:In Exchange Server 2003, the additional queue information shows the following status for the message:Additionally, you may see events that are similar to the following in the event log in Exchange 2000 Server:

Event ID 4000
Source: SMTPSVC
Type: Warning
Description: Message delivery to the remote domain 'domain.com' failed for the following reason: Unable to bind to the destination server in DNS.

In Exchange Server 2003, you may see events that are similar to the following event in the event log:

Event ID 4000
Source: MSExchangeTransport
Type: Warning
Description: Message delivery to the remote domain 'domain.com' failed for the following reason: SMTP could not connect to any DNS server.

These symptom may occur even if you add an SMTP connector and set it to forward e-mail messages to the address of a smart host.

This issue may occur if any one of the following conditions is true:

• External Domain Name System (DNS) servers are configured incorrectly for the default SMTP virtual server in Exchange. You can view the configuration settings on the Delivery tab in the Advanced Delivery dialog box of the default SMTP virtual server.
• The external DNS servers that are specified for the default SMTP virtual server are no longer available.
• The Secure cache against pollution option in Microsoft Windows 2000 DNS is enabled. If the Secure cache against pollution option is enabled, it can prevent the DNS server from following up DNS referrals.
  
  Important Do not disable the Secure cache against pollution option. Refer to the article in the "Workaround" section to deal with this issue.
• The DNS servers are unavailable.
• Networking issues (permanent or intermittent) are restricting access to the DNS servers.

To work around this issue, remove the external DNS server references in Exchange System Manager, and then restart Microsoft Internet Information Services (IIS).

To remove the external DNS server references, follow these steps:

1. Start Exchange System Manager.
2. If administrative groups are enabled, expand Administrative Groups, and then expand First Administrative Group.
   
   If administrative groups are not enabled, go directly to step 3.
3. Expand the Servers container, and then expand the Your_Server_Name container.
4. Expand the Protocols container, and then expand the SMTP container.
5. Right-click Default SMTP Server, and then click Properties.
6. Click the Delivery tab, and then click Advanced.
7. Click Configure, and then click the first entry in the External DNS list.
8. Click Remove.
9. Remove each remaining entry from the External DNS list.
10. Click OK three times.
11. Quit Exchange System Manager.

To restart IIS, follow these steps:

1. Open the Services snap-in.
2. Right-click the IIS Admin Service, and then click Restart.
3. In the Restart Other Services dialog box, click Yes to restart the dependency services.
4. Close the Services snap-in.

If the symptoms still persist after you remove the external DNS server references in Exchange System Manager, check the Networking issues and perform the steps that are described in the following article to resolve this issue.

For additional information about configuring SMTP in Exchange 2000, click the following link to download the Configuring SMTP in Microsoft Exchange 2000 Server book.

The following file is available for download from the Microsoft Download Center:
Download the SMTPConfigE2k.exe package now.
For information about configuring SMTP in Microsoft Exchange Server 2003, click the following link to download the Exchange Server 2003 Transport and Routing Guide.

The following file is available for download from the Microsoft Download Center:
Download the Ex2K3_Transport_Routing_Guide.exe package now.
For more information about how to download Microsoft support files, click the following article number to view the article in the Microsoft Knowledge Base: Microsoft scanned this file for viruses. Microsoft used the most current virus-detection software that was available on the date that the file was posted. The file is stored on security-enhanced servers that help prevent any unauthorized changes to the file.