<style type="text/css" media="screen">
  @media screen {
    /* Add all text elements used in your email template */
    body, div, p, li, th, td,
    a, strong, b, em, li, address,
    h1, h2, h3, h4, h5, h6 {
      font-family: 'Source Sans Pro', sans-serif !important;
    }
  }
</style>