Remember that promotional spot, for a certain cable TV network, which popularized the slogan, “Merlot and e-mail don’t mix”?

Now, GMail has instituted a new ‘feature’ for its users designed to save you – whether you’re in the heat of passion, the depths of a depression or the throes of exhaustion – from sending messages you might regret later.

The Official GMail Blog brings word today of Mail Goggles, designed to make you pause for sober second thoughts before actually sending a message.

When you enable Mail Goggles, it’s set by default to keep an eye on you during the wee small hours of the late night/early morning. But users can specify the days of the week and times of day when they want to be protected from themselves.

The operational concept behind Mail Goggles is simple. The system simply jumps in after you hit the send button making you solve what the lottery people call a ‘skill-testing question’ – a series of simple mathematical problems designed to make you focus mentally and give you a few moments to reflect on the advisability of the e-mail you just tried to blast out.

Mail Goggles is currently in beta. If you’re a GMail user, go have a look and give it a try. You may well thank yourself later!