Google unveiled a funny new feature for Gmail that aims to prevent you from sending mails you wish you hadn't. It's called Mail Goggles and it tests your state of mind by making you solve a couple of simple math problems:
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.