Almost three-quarters of firms are concerned about data leakage via e-mail, as half of employees admit to sending e-mails to the wrong person.
Web security firm Sophos, which carried out research into e-mail data leaks, said the problem potentially caused corporate embarrassment, compliance breaches and the loss of business critical information.
For its research, Sophos surveyed 200 firms and 300 employees online.
"The risk of slipping up and clicking 'send' without double-checking the recipient's details is ever-growing as e-mail use spirals in business," said Graham Cluley, senior technology consultant at Sophos.
Sophos recently announced its e-mail security appliances could now prevent the loss of corporate data through e-mail leaks.