It's happened to all of us. 

You hit "send" on an email and immediately regret it. Maybe you said something you instantly want to take back or perhaps you put "Mike M." in the address field when you meant "Mike R." Or even worse, maybe you hit "reply all" when you meant to just reply to the person who sent the message.

Jobs have been lost over mis-sent emails. Relationships have broken up over them and immeasurable damage has been done because email, once sent, can not be taken back. It's the old sitcom trope where someone drops a scathing letter telling off his boss into a mailbox just before learning of a promotion. In that old gag, the protagonist would fail trying to snake the letter out of the mailbox before the finale where he or she would try to steal the letter off the boss's desk.

But just like in the days of physical mail -- even more so, actually -- email cannot be taken back. 

Google (NASDAQ:GOOG) (NASDAQ:GOOGL) has just changed that for Gmail users.

What is Google doing?
After years of testing it in Gmail Labs, where it proved popular, an Unsend feature has been added to the Gmail inbox. The company explained how it works in a blog post.

'Undo Send' allows people using Gmail to cancel a sent mail if they have second thoughts immediately after sending. The feature is turned off by default for those not currently using the Labs version, and can be enabled from the General tab in Gmail settings.

It's almost stunning that an idea so simple has taken so long. It's not an endless failsafe -- users only have a short, adjustable countdown to change their mind -- but it's a cure for instant regret and a potential lifeline that could save someone from embarrassment or worse.

Source: Google

Why does this matter?
While every email provider including Google would like to tell users it has the best email, the reality is most major email providers are pretty similar. There are back-end differences and user interface differences, but whether you use Gmail, Outlook through Microsoft's Office 365, or something else, it's all a pretty similar user experience.

Adding the "Undo Send" button gives Google a major differentiator that could be the deciding factor in which service an individual or a business decides to use for email.

Google does not specifically break out revenue for Gmail, but in 2014 Google generated nearly all of its revenue -- $43.6 billion out of $46 billion -- from advertising. That's how it monetizes its email service as well. More Gmail customers means more ads served and the addition of this feature could very well bring in new users.

This is good for business
A single email can have huge repercussions. For example, in 2011, London-based trader Paul Moss allegedly sent an email saying that Greece would restructure its debt as soon as the weekend, The Daily Mail reported. That single email set off a panic which caused Greek bank shares to drop 4.6%.

It's impossible to know if Moss regretted the email and might have hit "Undo Send," but his actions literally affected an entire country.

Just Google "email disasters" and you'll find countless tales of people at work who accidentally sent their customers a reply meant only for their co-workers. This seems to happen a lot among the various financial firms and Wall Street brokers, but it's likely no company is immune.

This just makes sense
How often in life do we immediately regret saying something and wish for the ability to take it back? That is, of course, impossible in a real conversation, but Google has now made it a reality when sending email.

It's a game-changing feature that actually solves a problem. "Undo Send" can prevent embarrassment and even financial loss. It's a choice that is long overdue. The only negative is that we'll have fewer funny stories of other people's horrible email miscues to laugh about.