I've been using Mailstrom service on and off for years for bulk classifying my mail and some automated rules, but it seems like they haven't added anything new in years (I think they are focusing in some sort of iPhone app now) and I've tried to contact them to ask a couple things and they don't answer my emails.
So I've been thinking to make some sort of similar app to go through my mail metadata and make grouping and rules... "Delete this emails after a week, move all these others just when you receive them, send this others straight to the bin" with some extra smartness added.