That looks nice! I do have to say, though, that having the contact history automatically visible in a sidebar is incredibly useful. I would consider adding it as an option to your app. Having it available at a glance, versus having to click through to a different page, makes a huge difference. Em Client also lets me hover over a message in this sidebar to pop-up a small version of it, so I can see just what it said. It's very useful when writing someone to be sure what you've recently (or distantly) said to them. Removing steps to getting this information is vital.