You can set up Web Messaging so that when you reply to a message, the original message is automatically included in your reply; if you do this, the original message appears in the same text box as your reply. (The original message is editable, is flagged "Original Message," and shows the From and Date fields.)
From the Account Options... menu, select Set My Preferences.
On the User Preferences page, locate Replying and select Include original message or Don't Include original message .
Click the Save Changes button at the bottom of the page.