cake-contact-us/templates/email/html/confirmation.php

<p>
    <?= __d('cake_contact_us', "Hi {0}", isset($contactUsFormSubmission->name) ? $contactUsFormSubmission->name : '') ?>,
</p>
<p>
    <strong><?= __d('cake_contact_us', 'We have received your message. We will be in touch soon.') ?></strong>
</p>
<p>
    <?= __d('cake_contact_us', 'Thank you') ?>,
</p>