Topic Last Modified: 2005-11-18

The Microsoft® Exchange Server Analyzer Tool initiates an SMTP session with the Exchange server to validate that the proper Exchange SMTP verbs are listed. If the X-LINK2STATE verb is not listed, a warning is displayed.

The X-LINK2STATE verb is used by Exchange to update the link state tables on the routing masters. The link state tables record up-to-date information about the status of the SMTP links throughout the Exchange organization. Exchange uses this information to pick the lowest cost and most reliable routes when routing messages. This functionality is also referred to as "Intelligent Routing."

The X-LINK2STATE verb is required by Exchange for efficient routing, and is not used by other SMTP providers. As such, the functionality is provided in a file (xlsasink.dll) that is installed and registered by Exchange Setup.

There are two known reasons why this warning may be returned. First, some administrators may have disabled xlsasink.dll as a way to work around the intelligent routing functionality it provides. This is not a recommended best practice and will likely lead to performance and reliability problems. In this case, it is recommended that you reinstall Exchange on the affected computer to install and register xlsasink.dll.

Secondly, this warning may be returned if you are running an antivirus product that installs and uses its own SMTP protocol stack to scan messages. In this case, the antivirus software may run its own SMTP stack that intercepts and scans messages before they reach the Exchange SMTP stack. In this case, the antivirus SMTP stack is not using X-LINK2STATE verb. It is recommended that you run the antivirus software in a mode that does not require it to install its own SMTP stack on the Exchange server.

For more information about X-LINK2STATE and other proprietary verbs used by Exchange, see the Microsoft Knowledge Base article 812455, "Definitions of Verbs That Are Used Between 2 Exchange Servers" (

For more information about how to view Exchange command verbs and reinstall Exchange 2000 Server, see the Knowledge Base article 319885, "XCON: Messages Sent in the Exchange 2000 Server Organization Are Not Delivered" (

For more information about how to view Exchange command verbs and reinstall Exchange Server 2003, see the Knowledge Base article 822939, "Messages That Are Sent in the Exchange Server 2003 Organization Are Not Delivered" (