When responding to a message it is often good practice to include the
original message to which you are responding. Often it is not
necessary to include the entire message; summarizing the specific
points to which you are responding are sufficient. It is important to
properly attribute the original message. Many user agents facilitate
citing and attributing of the original messages. For example,
supercite (SuperCite, for details) provides
sophisticated citing and attributing of the original messages.