Replying to Emails
Include enough of the original message in your replies as it will help the recipient to place your reply in context. Quote back only the smallest amount you need to make your context clear. Use some kind of visual indication to distinguish between text quoted from the original message and your new text - this makes the reply much easier to follow. Pay careful attention to where your reply is going to end up: it can be embarrassing for you if a personal message ends up on a mailing list, and it's generally annoying for the other list members.
Sections in this articleIntroduction
What is an email
Formats, grammar and spelling
Addresses and personal names
Courtesy and politeness
Letter writing: Formal and informal