How does IMAGESPAM work ? Are there any settings

Hi there,

I had to unset the IMAGESPAM feature, since it tags as spam every mail that contains screenshots (for example). A one month survey shows that the false positive rate of this test is greater than 99% (please note that the aggressive mode was unset !) ! 

How does it works ? Is it tunable ? 

Since the false positive rate is above 99%, turning off the IMAGESPAM feature shouldn't cause issues. Anyway, I'd like to understand what the feature is usefull for ?

I've been unable to find any usefull information in the documentation.

Claude