case_class_server/common/mail/layouts/text.php

<?php

/** @var \yii\web\View $this view component instance */
/** @var \yii\mail\MessageInterface $message the message being composed */
/** @var string $content main view render result */

?>
<?php $this->beginPage() ?>
<?php $this->beginBody() ?>
<?= $content ?>
<?php $this->endBody() ?>
<?php $this->endPage() ?>