It's also handy for organizing your reply. If a correspondent makes several points in a message, you can insert your responses after each point. The latest version of America Online's software can do this, but it's almost a hidden feature. When you receive mail on America Online, highlight the text in the message you want to quote. When you hit reply, the highlighted text will be copied over at the top of the reply message field.
Quoted text is set off with a pair of angle brackets.
You can control how the quoting will appear by going to the Members menu, choosing Preferences, then clicking on Mail. When using quoted text, be judicious. And be sure to remove all extraneous items, such as headers and attached signatures. Chronicle computer columnist Dwight Silverman can help.