MIT’s Daniel Smilkov, Deepak Jagdish, and CÚsar Hidalgo have created a great Gmail metadata visualization tool called Immersion. The first thing that Immersion does is map your email interaction networks in a nice interactive way. You can see networks emerge, strength of ties (via number of interactions), isolated mail bombers (usually listservs or alerts), and relationships easily and beautifully.
For me this is particularly nice as you can control the time periods that are mapped. So I mapped my email interactions for the three years before I quit email, then the two years after having stopped doing email, finally the past month of #noemail (this past month).