At one time or another, we've all accidentally hit the send button on an email, or sent it to someone we didn't intend to. But this instance is particularly bad.

On Friday, more than 1,300 employees of London-based Aviva Investors walked into their offices, strolled over to their desks, booted up their computers and checked their emails, only to learn the shocking news: They would be leaving the company.

I am required to remind you of your contractual obligations to the company you are leaving, the email said. You have an obligation to retain any confidential information pertaining to Aviva Investors operations, systems and clients.

The email ordered them to hand over company property and security passes before leaving the building, and left the staff with one final line:

I would like to take this opportunity to thank you and wish you all the best for the future, said the letter.

This email was sent to Aviva's worldwide staff of 1,300 people, with bases in the U.S., UK, France, Spain, Sweden, Canada, Italy, Ireland, Germany, Norway, Poland, Switzerland, Belgium, Austria, Finland and the Netherlands. And it was all one giant mistake: The email was intended for only one individual.

About 25 minutes after the initial e-mail was sent, Aviva's HR department realized the error and recalled the email. Soon aftewards, Aviva released another email apologizing to the entire staff for its massive email gaffe.

An email which was intended for a member of staff who was leaving today was accidentally sent to all Aviva Investors staff worldwide, said Paul Lockstone, a spokesperson for Aviva.

Lockstone said that Aviva's quick actions to correct the issue ensured that no employees were truly offended.

People were pretty quickly aware of the fact that this was a mistake, Lockstone said. I don't believe any of our staff would have seen it really as anything other than the mistake that it was.

Shake-ups have been relatively common at Aviva, at least in recent weeks. Just two days prior, Aviva's CEO Andrew Moss said he would be overhauling the board and booting Alain Dromer, Aviva's corporate head, as well as the heads of Europe and North America, Igal Mayer and Richard Hoskins, respectively.

Aviva Investors is also restructuring its assets and employees, and said back in January that it looks to cut about 160 jobs -- roughly 12 percent of its global worldforce.

Aviva Investors is responsible for managing the funds of Aviva PLC, the sixth-largest insurance group in the world. Aviva Investors manages assets of more than $420 billion.