Go to the Preferences tab, E-mail options button and hit the spacebar. This button is the first button on the tab.

Tab 8 times until you hear "When forwarding a message, combo box. Use the alt+down arrow and the choice you want. If you select the "Prefix each message with " option tab to the Prefix with field. Delete the greater than sign. Tab to the Ok button and press the spacebar.

You will receive a message if you include prefix it will spell-check the whole message. Spacebar on Ok.

If you deleted the prefix category, you will see a message that you have chosen to prefix the original message, but have not selected a prefix character, is this ok? press the spacebar button.