According to Paul Rutherford, Legal Week, 06/03/2003, one irresponsible e-mail can be quickly broadcast to thousands of people and land a firm with a serious litigation claim.

"As with most office-based professions, the use of e-mail has become mandatory for those working in the legal industry. Yet many high-profile organisations have been forced into legal action against staff who use e-mail in an illegal or irresponsible manner. E-mail is a strange hybrid form of communication, which has all the informality of verbal communication yet all the permanence of a formal written letter. To make matters worse, it can easily be broadcast, inadvertently or maliciously, to hundreds — or even thousands — of people in a matter of seconds.

The potential cost of just one irresponsible e-mail finding its way to a sensitive employee, or being forwarded from within an organisation to a customer or partner, can be staggering. Litigation cases involving loss of confidentiality, harassment or dissemination of pornographic material can reach seven-figure sums.

When composing an e-mail you must make the assumption that, unknown to you, it may be read or distributed to more people than just the addressee.
This could, of course, happen with a letter, but it is the ease with which e-mail can be distributed that makes it so much more likely to be shared. So:

- Before you press the send button, review what you are sending and to whom it is going.
- Make a point of reviewing any attachments you are sending on — they may have been previously sent to you. Company confidential/client-sensitive information can ‘leak’ out of the practice inadvertently in this way.
- Do not forward virus hoaxes and chain letters and do not overuse ‘reply to all’.
- Do not use e-mail to send complaints about fellow employees or clients: e-mail is not the best forum for this and it could land your company in a lawsuit if it gets into the wrong hands.
- Always check the recipient box of the e-mail you are about to send — are there any recipients that you may have included by mistake?
- Try not to use company e-mail to send jokes and large attachments: it wastes productivity and eats up bandwidth, minimising network performance."

Source - www.legalweek.net.