Personaliza login de e-mail

Para WHM & CPANEL

HTML

<link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/4.0.0-beta.2/css/bootstrap.min.css">
<script src="https://code.jquery.com/jquery-3.2.1.slim.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/popper.js/1.12.3/umd/popper.min.js"></script>
<script src="https://maxcdn.bootstrapcdn.com/bootstrap/4.0.0-beta.2/js/bootstrap.min.js"></script>
<div class="container-fluid text-center">

  <div class="row">
    <div class="col-md-12" style="margin-top: 40px;">
      <img src="https://midia.oregionalsul.com.br/2017/11/cores-3.png" class="img-responsive center-block">
    </div>
  </div>

  <hr>


  <div class="row justify-content-md-center">

    <div class="col-sm-2">
      <!-- <h3>Formulário de acesso</h3> -->

      <!-- formulário-->

      <form action="login-webmail.php" method="post">

        <div class="form-group">

          <label for="user" class="form-text text-left">Conta</label>

          <div class="input-group mb-2 mb-sm-0">

            <input placeholder="Usuário" type="text" name="usuario" id="user" class="form-control form-control-lg" />
            <!-- <input type="text" class="form-control" id="inlineFormInputGroupUsername" placeholder="Username"> -->
            <div class="input-group-addon">@seudominio.com</div>

          </div>

          <small class="form-text text-muted text-left">Não insira @dominio, apenas conta.</small>

        </div>


        <div class="form-group">
          <label for="pass" class="form-text text-left">Senha</label>
          <input id="pass" placeholder="Senha" type="password" name="senha" class="form-control form-control-lg" />
        </div>

        <button id="acessar" type="submit" class="btn btn-success form-control">Acessar</button>

      </form>

      <!--  fim do formulário-->

    </div>
  </div>


  <hr>
  <div class="row justify-content-md-center">

    <div class="col-sm-4">
      <h4>Powered by <a href="#" target="_blank">O Regional Sul</a></h4>

      <p>O...