The version of SMTP running does not support the XEXCH50 verb

[This topic is intended to address a specific issue called out by the Exchange Server Analyzer Tool. You should apply it only to systems that have had the Exchange Server Analyzer Tool run against them and are experiencing that specific issue. The Exchange Server Analyzer Tool, available as a free download, remotely collects configuration data from each server in the topology and automatically analyzes the data. The resulting report details important configuration issues, potential problems, and nondefault product settings. By following these recommendations, you can achieve better performance, scalability, reliability, and uptime. For more information about the tool or to download the latest versions, see "Microsoft Exchange Analyzers" at]  

Topic Last Modified: 2009-09-14

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 XEXCH50 verb is not listed, a warning is displayed.

Among other things, the XEXCH50 verb is used by Exchange for public folder replication. Running a version of SMTP on an Exchange server that does not support the XEXCH50 verb will break public folder replication.

The XEXCH50 verb is not used by other SMTP providers; therefore, the functionality is provided in a file (peexch50.dll) that is installed and registered by Exchange Setup.

The Exchange Server Analyzer may return this warning 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 uses its own SMTP stack to intercept and scan messages before they reach the Exchange SMTP stack. In this case, the SMTP stack in the antivirus software is not using the XEXCH50 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 or run such software at the incoming perimeter of your SMTP network. If you have disabled the SMTP stack for the antivirus software, and you still get this warning, reinstall Exchange to install and register peexch50.dll properly.

For more information about XEXCH50 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 Server 2003, see the Knowledge Base article 822939, "Messages That Are Sent in the Exchange Server 2003 Organization Are Not Delivered" (


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