email+etiquette

What is proper email etiquette?
Professional email communication is different than personal email communication. When communicating with clients or instructors, one should use proper professional email etiquette:
 * 1) use a clear, concise, short subject
 * 2) address the recipient by name
 * 3) explain why you are writing the email
 * 4) keep your note brief and to the point
 * 5) specify what class you are in (if you are a student)
 * 6) close with a simple signature (if you are a student, just your name will be fine)
 * 7) do not format your email (i.e. bold, italics, color, all caps, etc)
 * 8) do not send attachments more than 1MB (images should be no wider than 1000px)
 * 9) when replying, include the text of the original note; do not change the subject
 * 10) when replying, stay on topic (or start a new email with a new subject)
 * 11) respond within 24 hours (if possible); it's ok to not respond on weekends
 * 12) use a professional email address (i.e. "sweetpea@hotmail.com" is not a good choice)

Also see Why should I switch to Gmail?