This is an interesting idea. Have you thought of using Sieve [1] to let people manage the rules directly from their mail client? Depending on how you set this up server-side it might not be possible, or indeed useful.
As a sysadmin my initial thought is that I would rather do this myself on a mail server I control, but I can definitely see value in both a hosted and on-premise version.
EDIT: I hope you don't mind some constructive criticism on the logo. Conceptually it works very well, but there is too much whitespace. I appreciate this is a landing page, so perhaps you have something else planned already.