Because of the convenience & speed of e-mail, people use it more frequently to communicate. There is no gesture, no tone, and no volume. There is no facial expressions intent, or emotions in an email. An E-mail is just words on paper from someone they have never met or only met a few times.
It is almost too easy to send e-mail with a negative emotional impact. Once you hit the send button and your e-mail goes charging across the Internet, you can't bring it back.
Sometimes, in the heat of the moment, you might be tempted to say something you would otherwise never say.
Sarcasm is particularly dangerous to attempt to convey in e-mail.
One way to help convey your meaning is through the occasional use of emoticons, also called "smileys." These are sets of plain text characters that are strung together to form little pictures, when read sideways. For example, :-) is obviously a smile and :-( is obviously a frown. Note the emotion by telling them to look at it sideways. Avoid the flashing, animated cartoon type of emoticons as many consider them tacky and they don't always display properly.
There are others but these are the most common don't get crazy people may find it offensive.
