Select the message you want to reply to and look at the very bottom on the right for the little box that says "Send Message", just start typing in that box (it expands as you type) when you finish typing you'll see the box to click to have it sent to you regular email if you want. Once you type something the little arrow on the far right will turn blue, click on that when you are ready to send the message.
Paranoia strikes deep
Into your life it will creep