Microsoft is developing a new “People View” feature for the Outlook Web App. The view will display emails based on “people who matter”. People View keeps track of your communications and brings the people who you interact with the most to the top of the priority list.
People whose messages you haven’t yet read appear higher in your list, and people whose messages you’ve already read appear lower in your list, so it’s easy to keep track of whom you still need to respond to.
The feature is coming to Office 365 and the Outlook web app over the next several months. No word yet on when it will be available in the desktop Outlook client.