I struggled too... I had concluded that this was a Chrome add-in to theme Gmail and add some extra analysis based on some off-Gmail server crunching some of the

I struggled too... I had concluded that this was a Chrome add-in to theme Gmail and add some extra analysis based on some off-Gmail server crunching some of the data from the email. But then I saw the post (below/above) which details the stack that they're using, and I think my assumption is probably wrong. I do think that you keep your own email address though.