is the default mail client of Gnome, providing integrated mail, calendar funcitonality and address book. The latest version avilable is which has been recently released.
installing Evolution 3.13.2 on Ubuntu 14.04 and derivative systems is easy. All you have to do is add the ppa to your system.
sudo add-apt-repository ppa:fta/gnome3
sudo apt-get update
sudo apt-get install evolution