The beginning of the end of a great civilization is the disappearance of simple good manners. In normal human interactions we recognize the need for some mutually agreed-upon rules of acceptable conduct. Often someone new to electronic mail and news groups will be so outraged that they will respond angrily.
People forget that once they push the button to send the mail, there is no retrieving it.
One should never put into a mail message anything that they would not like to see posted on a bulletin board with their name on it. When writing a message you should know that it is very easy for a message to get forwarded to a place you did not expect the message to go. In other words be careful what you say because it could get back to someone you do not want to read it. When forwarding messages try to cut out information that is not relevant to the conversation you are discussing. It is considered rude by some people to forward a message that you did not write without the permission of the person who wrote the message.