Hands-free mode not working on Samsung Galaxy SIII

I've activated Hands-free mode from the configurable set of switch-buttons at the top of the notification panel on my Samsung Galaxy SIII, and such mode also appears activated under Settings -> My device -> Hands-free mode. Such entry reads: "Incoming calls and new notifications will be read out automatically". However, I've tried sending myself e-mail messages and also received some WhatsApp messages, which triggered the Whistle Default notification sound and made the front Blue LED blink until I swiped down my notification panel. As I was saying, however I didn't hear any voice coming from the phone reading out the notifications aloud, so it seems like this feature is not working for me. What am I doing wrong? Thanks.