The concept behind InboxGuardian began in our eMailTrackerPro product and has taken the location feature forward to enhance its spam filtering ability.
Why is location important?
Email location allows you to quickly detect if an email is legitimate or not. Many phishing emails (emails that appear to be from your bank etc) can be easily caught using the location as an indicator.
For example if you receive an email that looks legitimate and is claiming to be from your bank yet the location says "China" then you know the email is going to a phishing email and you can immediatly discard it.