Yii2 why links in a mail letter flies?

Question

Yii

Hello! I can not understand why when sending mail letters in the letter the links become inactive. They lose the 'href' parameter
Letter example

<p>
  Ссылка для входа: <?= \frontend\helpers\Html::a(\yii\helpers\Url::home(true)) ?>
</p>

At the output I get:

<p>
  Ссылка для входа: <a>http://crm.topjam.ru/sk-orto/</a></p>

Answer 1

Probably the answer is in your custom helper, \frontend\helpers\Html::ahow do we know what its "a" method does? Can you show me the code for it?