Código pertinente:

msg = "Subject: Reset password instructions\n\nHello " + @request_payload["email"] + "!\n\n" +
      "A new account has been created for you at <a href=\"presentation-layer.dev\">presentation-layer.dev<a>." + 
      "Please go to that page and click \"forgot password\" to set your password."
      smtp = Net::SMTP.new 'smtp.gmail.com', 587
      smtp.enable_starttls
      smtp.start('domain', "email", 'password', :login) do
        smtp.send_message(msg, 'sender', "recip")
      end

El correo electrónico resultante solo contiene el texto en bruto. ¿Cómo consigo que el servidor evalúe las etiquetas HTML?