Hi,
Just take a look at the screen i attached. As the yellow arrow is pointing to, there's a small round button like radio button in the Contact master detail. when it is clicked, some menu option like adding to communicator/mailing/calling will be showed referring to the 2nd screen shot.
plus,
1, not every client pc shows this "button"
2, not every contact shows this "button"
Anyone knows what it is?