What does the Regtrace utility do?
Regtrace is a Microsoft specific tool that lets you troubleshoot routing and transport problems in Exchange 2000 Server. The utility works by logging what the routing engine and message categorizer are doing. Although the log that Regtrace generates is useless to the user, Microsoft Product Support Services (PSS) can use it to track decisions that the routing subsystem makes while processing messages.
Regtrace ships in the \support\utils\i386 folder of the Exchange 2000 CD-ROM. If you need to use the utility, PSS will tell you to install it on the server you're troubleshooting. Before Regtrace can trace anything, you must run the utility and tell it what to trace—the trace won't work until you add the list of modules whose behavior you want to trace. (For the complete list of modules, see the Microsoft article "XCON: How to Set Up Regtrace for Exchange 2000" at http://support.microsoft.com/?kbid=238614.) After you perform this step, you must add a new REG_MULTI_SZ registry value to the HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\MosTrace\CurrentVersion\DebugAsyncTrace registry subkey. No tracing output will be generated until you run Regtrace for the first time. After you turn on tracing, you can repeat the problem operation on your server, stop the trace, then send the resulting log file to PSS for analysis.