Hello,
I think it's just leftover from the days when I was trying to figure out how get spamassing working (very long time ago).. Not too sure what exactly it did, but it's in the package for the reason that, if its needed (for whatever reason) it's there. After doing a quick browse through it, it looks like it's just a perl filter to either send mail to a mailbox, or to a spam inbox in /var/spool/spam. Not sure that this would be of any use to a server with hundreds of accounts.
John