The GWIA Log Utility is designed to give a rough overview of the messages that the GWIA is passing. You will get a rough idea of the daily traffic and can keep an eye on the email addresses passing through it.
For instance, it has helped me identify spammers allowing me to block them outside of my network. It has also alerted us to employees who are abusing their Internet email usage. One hourly employee wrote 700 emails over the course of the month and their job required little to no Internet email. We have even identified problems with addressing: I found a number emails that were sent with increasing frequency to an incorrect, by one letter, email address. An email to the sender alleviated a potentially ugly situation.