We've all had that sinking feeling, when you realize you've sent an email to the wrong person or published a private conversation to your entire company by hitting the reply all button in error.

Millions of people around the world may be able to untie that knot in their stomach thanks to unSend.it, which claims to delete all traces of those unwanted mails. It just might be a few years too late for Hillary Clinton.

There are, however, other services that claim to be able to retrieve mails. For instance, Gmail has an "unsend" button and Outlook has a similar service, but both only work in certain circumstances. Gmail's unsend button is only available temporarily and only works for emails sent on Google's servers. Outlook's "recall" button only works when the recipient is on the same Microsoft Exchange email server. So, is unSend.it any different?

Well, yes and no. UnSend.it can delete emails but using the service seriously limits the type of emails you can send. The text in emails, once they've left your server, cannot be retrieved but images work slightly differently — they are remotely downloaded from a server and can be deleted.

When you send an email through unSend.it, your message is converted into a JPEG image and embedded in the email body. That allows users to "unsend" their messages by deleting or editing and replacing this image. There is also tracking data built into the images that allows you to see who, if anyone, has read your mail.

This is great if it works, but there are a few fundamental problems. First and foremost is that many email servers block messages with images. There's no point in being able to delete mails if they never arrive in the first place. All the emails sent with the service contain an irremovable signature advertising unSend.it as "Regret-Free Emailing" which, presumably, you won't want to accompany every message you send.

There are also heightened security concerns when sending images rather than text. The interface is also hardly up to modern day email client standards. Admittedly, unSend.it is only in beta, but users can't even cc recipients or attach files to emails. There is, however, an option of sending Gmail messages through unSend.it servers.

So, unSend.it could work for sending certain emails, but unless all your emails have the "unsend" function, it kind of defeats the purpose as you never know ahead of time when you're going to make the mistake.

It's a nice concept, but unfortunately unSend.it isn't the answer to a problem that has been cursing people since the dawn of email, and it is unlikely to work as well as in the demo video below.