A study by market research firm Radicati Group has shown that over one in 20 employees has sent company secrets to third parties via email.
The Corporate Email User Habits study found that a quarter of those surveyed had forwarded corporate email to their personal accounts for later use, and nearly two thirds use their personal email for company business.
"While six per cent may seem like a small number, in a 10,000-user organisation it translates to 600 employees leaking intellectual property," said Sara Radicati, president of the Radicati Group.
"It only takes one email to leak critical trade secrets to cripple an organisation's business strategy.
"Companies should take a hard look at educating their workforce on its official email policy, and put in place outbound filtering and monitoring technology that can block confidential or sensitive emails before they leave the corporate network, as well as report violations."
Only 22 per cent of companies surveyed had any policy on monitoring outgoing mail, and only half had any kind of internal policy regarding email use.
The survey also highlighted the increasing problem of offensive email. Seven out of 10 respondents said they had received offensive email, 42 per cent of which had come from within the company.
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