New feature for version 3.1

You can create HTML template for emails which sends from app. Go to "Configuration / Email Options / Email layout" and turn HTML layout ON. 

Use tag ${body} to insert message content in html.

You can use code bellow as baseline for your html email. Your email will look like this:

For more information about Responsive HTML Email see https://github.com/leemunroe/responsive-html-email-template

<!doctype html>
<html>
  <head>
    <meta name="viewport" content="width=device-width, initial-scale=1.0"/>
    <meta http-equiv="Content-Type" content="text/html; charset=UTF-8" />
    <title></title>
    <style>
      /* -------------------------------------
          GLOBAL RESETS
      ------------------------------------- */
      
      /*All the styling goes here*/
      
      img {
        border: none;
        -ms-interpolation-mode: bicubic;
        max-width: 100%; 
      }

      body {
        background-color: #f6f6f6;
        font-family: sans-serif;
        -webkit-font-smoothing: antialiased;
        font-size: 14px;
        line-height: 1.4;
        margin: 0;
        padding: 0;
        -ms-text-size-adjust: 100%;
        -webkit-text-size-adjust: 100%; 
      }

      table {
        border-collapse: separate;
        mso-table-lspace: 0pt;
        mso-table-rspace: 0pt;
        width: 100%; 
      }

      table td, table th {
          font-family: sans-serif;
          font-size: 14px;
          vertical-align: top; 
          text-align:left;
      }

      .table-item-details td, .table-item-details th{
          border-bottom: 1px solid #f6f6f6;
      }

      /* -------------------------------------
          BODY & CONTAINER
      ------------------------------------- */

      .body {
        background-color: #f6f6f6;
        width: 100%; 
      }

      /* Set a max-width, and make it display as block so it will automatically stretch to that width, but will also shrink down on a phone or something */
      .container {
        display: block;
        margin: 0 auto !important;
        /* makes it centered */
        max-width: 680px;
        padding: 10px;
        width: 680px; 
      }

      /* This should also be a block element, so that it will fill 100% of the .container */
      .content {
        box-sizing: border-box;
        display: block;
        margin: 0 auto;
        max-width: 680px;
        padding: 10px; 
      }

      /* -------------------------------------
          HEADER, FOOTER, MAIN
      ------------------------------------- */
      .main {
        background: #ffffff;
        border-radius: 3px;
        width: 100%; 
      }

      .wrapper {
        box-sizing: border-box;
        padding: 20px; 
      }

      .content-block {
        padding-bottom: 10px;
        padding-top: 10px;
      }

      .footer {
        clear: both;
        margin-top: 10px;
        text-align: center;
        width: 100%; 
      }
        .footer td,
        .footer p,
        .footer span,
        .footer a {
          color: #999999;
          font-size: 12px;
          text-align: center; 
      }

      /* -------------------------------------
          TYPOGRAPHY
      ------------------------------------- */
      h1,
      h2,
      h3,
      h4 {
        color: #000000;
        font-family: sans-serif;
        font-weight: 400;
        line-height: 1.4;
        margin: 0;
        margin-bottom: 30px; 
      }

      h1 {
        font-size: 35px;
        font-weight: 300;
        text-align: center;
        text-transform: capitalize; 
      }

      a {
        color: #3498db;
        text-decoration: underline; 
      }

      hr {
        border: 0;
        border-bottom: 1px solid #f6f6f6;
        margin: 20px 0; 
      }

      /* -------------------------------------
          RESPONSIVE AND MOBILE FRIENDLY STYLES
      ------------------------------------- */
      @media only screen and (max-width: 620px) {
        table.body h1 {
          font-size: 28px !important;
          margin-bottom: 10px !important; 
        }
        table.body p,
        table.body ul,
        table.body ol,
        table.body td,
        table.body span,
        table.body a {
          font-size: 16px !important; 
        }
        table.body .wrapper,
        table.body .article {
          padding: 10px !important; 
        }
        table.body .content {
          padding: 0 !important; 
        }
        table.body .container {
          padding: 0 !important;
          width: 100% !important; 
        }
        table.body .main {
          border-left-width: 0 !important;
          border-radius: 0 !important;
          border-right-width: 0 !important; 
        }

      }

    </style>
  </head>
  <body class="">
    
    <table role="presentation" border="0" cellpadding="0" cellspacing="0" class="body">
      <tr>
        <td>&nbsp;</td>
        <td class="container">
          <div class="content">

            <!-- START CENTERED WHITE CONTAINER -->
            <table role="presentation" class="main">

              <!-- START MAIN CONTENT AREA -->
              <tr>
                <td class="wrapper">
                    <h2>Company Name</h2>
                    <hr>
                                    
                      ${body}
                                    
                    <hr>
                    Some custom text in body...
                </td>
              </tr>

            <!-- END MAIN CONTENT AREA -->
            </table>
            <!-- END CENTERED WHITE CONTAINER -->

            <!-- START FOOTER -->
            <div class="footer">
              <table role="presentation" border="0" cellpadding="0" cellspacing="0">
                <tr>
                  <td class="content-block">
                    You company address here<br>
                    If you have any question please contact us <a href="https://www.rukovoditel.net/contact_us.php">contact us</a>.
                  </td>
                </tr>
                <tr>
                  <td class="content-block">
                    Powered by <a href="https://www.rukovoditel.net">www.rukovoditel.net</a>.
                  </td>
                </tr>
              </table>
            </div>
            <!-- END FOOTER -->

          </div>
        </td>
        <td>&nbsp;</td>
      </tr>
    </table>
  </body>
</html>