I like the way kube will go gread job here is my example of the mail overview and the detail view for mail conversation on phone/tablet.
For the Avatars I also have some additional stuff in mind like company logo, heart layout for the girlfriend(s), ...
I you think it's a git layout, yes the overview of the mail conversation show each mail as icon and you can fork the conversation. A really good thing to get an overview off a conversation thread.