I do not host my mail (unfortunately) because my ISP ( ) blocks my port 25 (god why can't I create an MX record with another port...*sob*), so I have a Windows-using friend hosting it for me. His mail server isn't powerful at all, and doesn't have any filtering ability.
I was wondering if procmail could filter my mail while Fetchmail downloads it, or if I'd need an MTA installed locally?