The revelation that top executives at oil giant Royal/Dutch Shell were writing bitchy emails to each other ahead of a financial scandal that would rock the City caused bemusement, and no doubt plenty of amusement, to many.

What were they thinking of? The now ousted chairman Sir Philip Watts, responding to an email from the (also ex-) head of exploration and production, Walter van de Vijver, warning about a breach of reserves accounting, wrote that he must leave 'no stone unturned' to get a 100% replacement ratio.

Van de Vijver later emailed that he was 'becoming sick and tired about lying abut the extent of our reserves issues'. On another occasion he even messaged a member of staff, concerning the same problem, to say: 'This is dynamite, not at all what I expected and needs to be destroyed.'

There is an acute irony in this executive urging that something be destroyed, when he was creating the very words that would not be - or could not be - destroyed and would help in his downfall.

Legion of embarrassments

In the comparatively young life of the internet, cases of embarrassing or incriminating emails are legion.

The best known is perhaps that of the benighted Claire Swire, who found discussions of her sexual practices with her boyfriend halfway round world cyberspace thanks to forwarding by friends of friends and colleagues.

Swire's indiscretion is perhaps excusable. She was not in a particularly senior position at work and even in three or four years the internet 'learning curve' has risen sharply. But top businessmen guiding the fortunes of multi-billion pound companies?

Shell is not alone among large organisations in producing emails that would return to torture their senders. They strike at the very heart of government. There was, for example, the notorious message from Jo Moore, a special adviser in the Department of Transport, suggesting that September 11 was 'a good day to bury bad news'. The prime minister's own spokesman, Tom Kelly, described a row with the BBC as 'a game of chicken'. And Jonathan Powell, No 10 chief of staff, revealed doubts about the strength of the evidence in the government's Iraq dossier.

For this reason, the government announced that from 2004, all emails from government departments would have to be sent to the Public Record Office at Kew. Emails would be treated in the same way as memos and other paper communications.

Informal and immediate

Now government staff are being encouraged to follow the example of the White House and use sticky Post-it-style notes that can be destroyed without a trace.

During the Enron investigation, more than 1.5m electronic messages were posted on the website of the federal energy regulator. Many were described as 'of an extremely personal nature', others just trivial, such as one discussing a windsurfing holiday. Doubtless no one expected any of these to get into the public domain.

Part of the problem is the nature of emails themselves, says Nick Fieldhouse, of law firm Stevens & Bolton. 'Emails are seen as informal and immediate, rather like the phone. They're not seen as legal documents, but they are.'

This view is supported by a government insider, who was recently quoted as saying: 'The problem is people inside Downing Street use email like an extension of a verbal conversation. They are much more candid in their choice of language than they would be in an official minute or note.'

He added: 'Generally, emails are dashed off by busy people at the speed of light. They're only intended to convey a quick thought or message to a close colleague, not leave a permanent incriminating record for all to see.'

Forwarding frenzy

Another problem, as Claire Swire found to her cost, is that electronic messages are routinely passed on to a third person, usually with the original message, or 'history', attached, says Fieldhouse. A message intended as a one-to-one communication 'can be flipped across the world in seconds'.

This leads to the other danger of defamation. The law here is no different from prevailing laws regarding written matter, but the chances of exposure are greatly increased. You can insult someone all you like, provided the communication is strictly one to one. If a third party gets involved, there is then a danger of libel.' In a serious case, this can lead to instant dismissal,' says Fieldhouse.

And it is not just the sender who is liable to a defamation charge. The employer and internet service provider are also at risk.

There are other difficulties. A misspelling of an email address can lead to an unconnected third party receiving it, or worse, the accidental inclusion of an address can mean sensitive information going to parties involved in negotiations or litigation with the sender.

He adds: 'People get the idea that because IT is relatively new, it's unregulated. Not a bit of it. It's more regulated. Not only do all existing laws apply, but there's an added layer of IT law on top. You're grossly regulated.'

Yet another trap is the abiding belief that you can erase an email. You can press as many 'delete' buttons as you like, but the chances are your message is still out there somewhere in cyberspace. 'It's an impossible task. A good computer expert can always trace what you've written from the hard drive.'

There were even rumours that a new product launched last year by Microsoft, Office 2003, would include a mechanism allowing an email to 'self-destruct' after a certain period. But, as the company pointed out: 'After a time limit an email doesn't vanish - it expires. Someone with administrative rights can always retrieve it.'

Foolishness

So, the question arises: with this knowledge, why do the great and the powerful, in boardrooms and centres of government across the world, continue to entrap themselves in such a foolish way? 'There's a power thing,' says Fieldhouse. 'They're used to talking to staff how they like. It would never occur to them they could say something others would find contemptuous. They're in their own world.'

In addition, he says, 'it's a natural human trait' to want to be relaxed and informal at times. 'You can't be on your mettle all the time.'

AVOIDING EMAIL HELL

1. Make sure you have a clear office policy about the use of emails.

This should include who is or is not authorised to send messages and whether or not personal messages are proscribed. But flexibility is also important to prevent a 'Big Brother' situation.

2. While emails may be informal or 'chatty', they should not be too slangy - and never use crude language.

3. Do not insult or make allegations about the person you are writing too - or any third party. A defamation suit could get you - and your company - in deep trouble. Remember that the employer and the internet service provider are equally as at risk as you.

4. Re-read your messages before you send them. There may be ambiguities that could cause offence unintentionally.

5. Never send sensitive information via email. Methods such as post or telephone are safer.

6. Be careful to check the spelling of the intended email address to avoid information getting into the wrong hands. Putting too many names in your 'cc' box could also mean too many people getting hold of things they shouldn't.

7. You should also check that email you have received has actually been sent by the person whose name is at the bottom. Hackers often send communications which look like they are from someone else.