I'm sure they could process exported gmail data dump: https://www.google.com/settings/takeout https://www.google.com/settings/takeout An analogy would be this

I'm sure they could process exported gmail data dump: https://www.google.com/settings/takeout https://www.google.com/settings/takeout An analogy would be this social graph network analysis tutorial which walks you through exporting your Facebook social graph data and creating cluster graph on it using a tool called Gephi: https://www.youtube.com/watch?v=kbLFMObmLNQ https://www.youtube.com/watch?v=kbLFMObmLNQ