You can easily reply to the sender of an incoming message without having to create a new message from scratch.

With the test message current, select Reply from the Message menu or press the Reply button to initiate a reply to the message.

A new composition window is displayed, with the sender’s address (in this case, your own) automatically placed in the To field of the header. The original sender’s text is automatically included in the body of the message. You can edit this text as needed (or it can be deleted by pressing the Delete key). You can enter more text in the reply message just as in any outgoing message. In your test reply, move the insertion point to the area below the original message and type in some additional text. To send this message, click Send.

Continue on to Transferring Messages Between Mailboxes