FIltering Problems

I have heard people say this filtering is "fantastic" so I must be missing something because is seems to me to be hopeless at stopping spam. If I have a hundred words or phrases I assume I have to enter each one as a separate rule and as the rules are case sensitive the combinations for the input for those hundred words must run into the thousands. I know I can use the regex thing but I have found that overcomplicated and ineffective and still run into the problems of case sensitivey. If it catches a genuine email I have no way of knowing what rules was triggered so fixing he problem is almost immpossible. The oulook rules are very simple to use and work well but I want to stop spam at the filter rather than have to download.