The POP3 Connector log files on SBS 2011 & SBS 2008 are stored in the following location:
C:\Program Files\Windows Small Business Server\Logs\pop3connector\Pop3service.log
If you wish to create a new log file you will need to stop the Windows SBS POP3 Connector service, rename the log file to something suitable, and then restart the service. A new log file will be created.
IT Consultant & Microsoft Licensing Solutions Specialist