[otrs] Filter spam using headers?

Hi, I have 1.3.2 installed and I want to be able to filter spam into a spam queue. We use SpamAssassin on the smtp server and it outputs the following headers into each message: X-Probable-Spam: yes/no X-Spam-Score: any number of *'s Assuming I've set up a "Spam" queue, how can I set OTRS up to filter X-Probable-Spam:yes and/or X-Spam-Score: *** (a certain number of *'s) into the spam queue and not auto-respond. I've tried modifying the PostMaster::PreFilterModule but I don't think I did so correctly and I think there must be another file that needs to be modified. Thanks, Jeff