I've never seen a good system to differentiate between legitimate transactional email and spam. Both produce high-volume, templatey mail. So how do we make su

I've never seen a good system to differentiate between legitimate transactional email and spam. Both produce high-volume, templatey mail. So how do we make sure that "Vi@gr@ Pilules from C@nada" pays 15 cents per message, without bankrupting the legitimate invoices, tracking updates, mailing lists, and legitimately requested advertising flyers?