In this case? Hope you have a record of all your filters, then re-implement them using Python's POP or IMAP library. If they fold after demonstrating significant market interest, I'd be happy to set up a competing service with improved usability and monetization.

It's not something I'd try to launch otherwise. I'd be more about a B2B service which aims to improve issue tracking, response times, and accountability. If that does well, go on to work on knowledge retention and retrieval, which is pretty much a giant black hole you can play in forever.