At a command prompt, type regtrace. The Trace Settings window opens.

On the Traces tab, select all the check boxes.

Traces tab of Trace Settings properties

On the Output tab, make sure that the File option is selected, and then provide a path to a location that has enough capacity to store a very large file as output.

On the Threading tab, make sure that the Write traces on a Background Thread option is not selected, and then click OK.

In Registry Editor, locate the following registry key:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\MosTrace\CurrentVersion\
DebugAsyncTrace

On the Edit menu, click Add Value, and then add the following registry values:

Value Name: Modules
Data Type: REG_SZ
Value:   AQ
         CAT
         DS2MB
         dsevntwrap
         EXSINK
         IMAP4SVC
         REAPI
         RESVC
         Routing
         SMTP
         StoreDev
         TranMsg
         DSACCESS

Next, add the MaxTraceFileSize registry key value to set the maximum trace file size to 20 megabytes (MB). On the Edit menu, click Add Value and add the following:

Value Name:   MaxTraceFileSize
Data Type:   REG_DWORD
Value:   20 (decimal)

Quit Registry Editor.

Reproduce the issue that you are troubleshooting. For example, if mail is being returned as undeliverable, send some e-mail messages to an address that will cause Exchange to return the message undelivered.

When you have reproduced the issue several times, stop tracing. In Regtrace, click the Output tab and select No Tracing.