Writing Effective Messages
Email is not the same as talking to someone face-to-face or even over the telephone. When we talk face-to-face, we pick up meaning from facial expressions, body language, specific gestures, and, of course, tone of voice. Even telephone conversations preserve the meanings conveyed by tone of voice. But email messages lose these extra ways of conveying meaning as we exchange messages, and so writers need to take care when writing email messages, even though they seem impromptu or off-the-cuff.
The best general advice: What you include in your email message depends on why you are writing and to whom. Effective email messages are short and to the point. Receivers don't want to scroll through two or more screens of text to get your message. On the other hand, don't make your messages so short that the receiver doesn't understand you. Provide enough information so that the receiver understands both the context and the details of the message.