Maintenance and Troubleshooting	<<	>>

Non-Delivery Reports

When Microsoft Exchange Server or a gateway is unable to deliver a mail message, it sends an NDR to the originator. The reason for the return is written below the recipients list in the report.

If the problem is not resolved, consult the Windows NT application event log, or create an SMTP log. For more information, see Chapter 4, "Troubleshooting Tools and Resources."

The recipient was not found.

Reasons Actions

There is no such address in the network or in the domain of the gateway host. Verify the address and the mapping of the address to a host.

The address was not unique. Verify the address. Make sure that all addresses in your network are unique.

The address was a phrase in several addresses but not an entire address of any mailbox. Have users press CTRL+K to verify the address before sending.

Reasons	Actions
There is no such address in the network or in the domain of the gateway host.	Verify the address and the mapping of the address to a host.
The address was not unique.	Verify the address. Make sure that all addresses in your network are unique.
The address was a phrase in several addresses but not an entire address of any mailbox.	Have users press CTRL+K to verify the address before sending.

The host is unreachable.

Reasons Actions

The receiving host is not operating. Set up or consult a link monitor to verify that the receiving host is operational, and then retry.

There is no such host in the domain or the domain does not exist. Check the IP address in the DNS table. Verify that all e-mail domain address names are spelled correctly in the DNS.

Reasons	Actions
The receiving host is not operating.	Set up or consult a link monitor to verify that the receiving host is operational, and then retry.
There is no such host in the domain or the domain does not exist.	Check the IP address in the DNS table. Verify that all e-mail domain address names are spelled correctly in the DNS.

Arguments are missing.

Reason Actions

The Internet Mail Service generated a protocol error. Check the Windows NT application event log for errors from MSExchangeIMC.
Create an SMTP log and look for the error. Error codes are explained in Requests for Comments (RFCs) 821, 822, and 1521. For more information, see Chapter 4, "Troubleshooting Tools and Resources."

Track the message in the message tracking log.

Reason	Actions
The Internet Mail Service generated a protocol error.	Check the Windows NT application event log for errors from MSExchangeIMC. Create an SMTP log and look for the error. Error codes are explained in Requests for Comments (RFCs) 821, 822, and 1521. For more information, see Chapter 4, "Troubleshooting Tools and Resources." Track the message in the message tracking log.

The time has expired.

Reason Actions

The Internet Mail Service established a connection to an SMTP host, but the host did not respond to any communication. The time delay for retries exceeded the threshold set for the Internet Mail Service. Verify that the host is operational. If necessary, increase the message time-out threshold in the Internet Mail Service Connections property page.
Run a Telnet to port 25. At the command prompt, type telnet hostname 25, and then type quit.