accounts/api/mails/current-email-confirmation-html.php

<?php
/**
 * @var string $key
 */
?>

<p>
    You want to change you account E-mail. Right? So you must pass the code below into field on site.
</p>
<p>Code: <?= $key ?></p>

<br />

<p><i>// P.S. yes, this is E-mail is not designed yet :)</i></p>