Lotus Notes Traveler logs errors and other information to text files in the \traveler\logs\ directory located under the Domino data directory.
Normally you have to go to this directory, select the file containing the information you want to examine and open the file with a text browser.
For troubleshooting issues it would be better, if you could see the log output at the moment the error occurs. To do so, you can use tail.exe from the Windows Server 2003 Resource Kit Tools.
The Microsoft® Windows® Server 2003 Resource Kit Tools are a set of tools to help administrators streamline management tasks such as troubleshooting operating system issues, managing Active Directory®, configuring networking and security features, and automating application deployment.
Create a .bat or .cmd file and call tail.exe along with the log file using the -f option.
D:\programme\IBM\Lotus\Domino\tail.exe -f D:\Programme\IBM\Lotus\Domino\data\traveler\logs\NTSActivity_0.log
Now you can watch the log file content in realtime.