About every hour I receive an email message stating 'RASExpress Server at 137.xxx.xxx.xxx has log file full'.

This is because you may be set up to send an email notification when log the file is created every hour, even if the log file is not full, it is still created every hour even when there is no activity. And at every hour, it will send out the log file.
You can turn this off if you do not want to receive the log files.