Microsoft KB Archive/276347

= XFOR: Messages Moved to the Badmail Folder When SMTP Service Forwards to Smart Host =

Article ID: 276347

Article Last Modified on 10/28/2006

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APPLIES TO


 * Microsoft Internet Information Server 4.0
 * Microsoft Internet Information Services 5.0

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This article was previously published under Q276347



SYMPTOMS
When the Simple Mail Transfer Protocol (SMTP) virtual server is configured to forward messages to a specific mail host, messages that are queued for outbound mail delivery are sent immediately to the Badmail folder. Because the SMTP service cannot deliver to the message originators, non-delivery reports (NDRs) are also sent to the Badmail folder.



CAUSE
This problem can occur if the DNS server that you have configured under Transmission Control Protocol and Internet Protocol (TCP/IP) properties does not support TCP queries.



RESOLUTION
To problem this behavior, use the appropriate method in this section.

Resolution for Internet Information Service (IIS) 5.0
 Start the Internet Services Manager. Right-click the server that has the SMTP virtual server configured, and then click Properties. Click the Delivery tab, and then click Advanced. In the smart host entry, make sure that you are not using the fully qualified domain name (FQDN) of the remote SMTP server.

The FQDN should not be used if the queried DNS server does not support TCP queries. Instead, type an Internet protocol (IP) address surrounded by brackets, for example:

[192.168.2.25]

The brackets cause messages to be forwarded directly to the IP address and prevent a reverse DNS lookup from being performed. Click OK, click OK, and then restart the SMTP virtual server.

Resolution for Internet Information Server (IIS) 4.0

 * 1) Start the Internet Services Manager.
 * 2) Click the server that has the SMTP site configured, and then click Properties.

NOTE: This server is the same as the SMTP virtual server.
 * 1) Click the Delivery tab.
 * 2) In the smart host entry, make sure that you are not using the FQDN of the remote SMTP server.

The FQDN should not be used if the queried DNS server does not support TCP queries. Instead, type an IP address surrounded by brackets.
 * 1) Click OK, and then restart the SMTP site.

Alternatively, you can change the currently configured DNS server to one that responds to TCP queries.
 * 1) In the TCP/IP settings of network properties, click the properties of the local area connection that you are using.
 * 2) Click Internet Protocol (TCP/IP), and then click Properties.
 * 3) Add a preferred DNS server that responds to TCP queries.

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STATUS
Microsoft has confirmed that this is a problem in the Microsoft products that are listed at the beginning of this article.

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MORE INFORMATION
Most programs use User Datagram Protocol (UDP) queries to resolve host names. When the contents of the query are larger than the maximum packet size, the program must use TCP.

The SMTP service is unique because the SMTP service uses TCP queries by default. If the DNS server does not support TCP queries, the query attempt resets. Therefore, the lookup for mail delivery does not respond and the messages are sent to the Badmail folder.

Request for Comments (RFC) 883 and the later RFCs recommned that DNS servers should be able to accept both TCP virtual circuits and UDP.

Additional query words: NDR badmail smtp iis mailhost

Keywords: kbprb KB276347

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