This is a crazy feature of gmail. Its designed to help you avoid embarrasment just in case you get drunk, emotional and then login to Gmail and decide to express your feelings to your boss or whoever. Fairly easy to setup. Go to settings -> labs and enable the option. Then select the times when you are most likely to get emotional / drunk / etc, and that’s it. When you hit send, you’ll have 60 seconds to answer 5 mathematical questions. If you get them wrong… it’s “water and bed for you”.