<header.php>

<li class="nav-item nav-dropdown">

            <a class="nav-link nav-dropdown-toggle" href="#"><i class="icon-envelope"></i> Emails</a>

            <ul class="nav-dropdown-items">

              <li class="nav-item">

                <a class="nav-link" href="single_mail.php"><i class="icon-envelope-open"></i> Single mail</a>

              </li>

              <li class="nav-item">

                <a class="nav-link" href="bulk_mail.php"><i class="icon-envelope-letter"></i> Bulk mail</a>

              </li>
            
 <li class="nav-item">

                <a class="nav-link" href="sent_mail.php"><i class="icon-envelope-letter"></i> Sent mail</a>

              </li>
            

            </ul>

          </li>

</header.php>
