index.html

<div class="form-group">
  <label for="exampleName">メールアドレス</label>
  <input name="email" type="email" id="email_addr" required />
  <small id="emailHelp" class="form-text text-muted">必須</small>
</div>
<div class="form-group">
  <label for="exampleName">メールアドレス（確認）</label>
  <input name="email_addr_repeat" type="email" id="email_addr_repeat" required />
  <small id="emailHelp" class="form-text text-muted">確認入力</small>
</div>