There's a startup called Etacts whose software can import your email (headers), and give you a view by person instead of by message. This is pretty obviously something you'd like to be able to see, if you have any significant volume of correspondence or correspondents. And it's pretty obviously a large leap of faith to give some random startup the ability to log into your email account.  

But, even more, this is a perfect example of something you ought to be able to do, at least basically, with your data without needing any extra application. Etacts provides some unique contact-management features, but the fundamental function of rotating data to some other axis is, I contend, rightfully a property of the data. You already own the view of your email by recipient, because it is immanent in your email. But your email service probably doesn't let you see it. I would like it to be the responsibility of a data-holding service to give you full logical access to that data.  

This is a huge part of why my work project matters to me. It is my attempt to design a universal data-modeling paradigm, and associated query-language, that could be a candidate standard for what it means to provide "full logical access" to data.