How to Enable Logging for IIS SMTP Server in Windows Server
If you have the SMTP feature installed (an SMTP server that works through IIS), logging is not enabled by default. To enable logging, perform the following steps:
Click on Start > Administrative Tools > Internet Information Services (IIS) 6.0 Manager. Expand your SMTP server and right click on your SMTP Virtual Server. Choose Properties:
Check "Enable logging" and click on Properties:
The log file directory is where the logs will be stored. In this case, it is C:\Windows\System32\LogFiles\SmtpSvc1\exyymmdd.log. Click on the Advanced tab to configure logging:
For the most detailed logging, check everything and click ok:
Logging is now enabled.