When crafting an e-mail message, always keep in mind that the receiver cannot hear your tone of voice or notice your body language. Be aware of the potential for misinterpretation, and create your message with the recipient in mind. By re-reading, you may be able to avoid misinterpretations.
Just remember, e-mail can not be equated to conversation. E-mail presents information in one dump, without any feedback. You can not see the body language that allows you to “read” the recipient, adjust your tone or respond differently. That is why it is unfortunately misread and misinterpreted regularly.