mail-account-admin/templates/includes/form_result_box.html.twig

{% if success is defined %}
    <div class="success_box">
        <h4>Success</h4>
        {{ success | raw }}
    </div>
{% elseif error is defined %}
    <div class="error_box">
        <h4>Error</h4>
        {{ error | raw }}
    </div>
{% endif %}