Gmail can't always prevent you from sending messages you might later regret, Jon Perlow has released a new Labs feature called “Mail Goggles” which may help you. When you enable Mail Goggles, it will check that you're really sure you want to send that late night Friday email. And what better way to check than by
making you solve a few simple math problems after you click send to verify you're in the right state of mind? By default, Mail Goggles is only active late night on the weekend as that is the time you're most likely to need it. Once enabled, you can adjust when it's active in the General settings.