<div class="mail-style1">
<div class="input-group">
    <input id="mc4wp_email" class="form-control input-newletter" name="EMAIL" required="required" type="email" placeholder="Enter your email..." /> 
    <span class="input-group-btn"> 
      <input class="btn btn-default" type="submit" value="sign up" />
    </span>
  </div>
</div>