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

{% if success is defined %}
    <div class="success_box">
        <h4>Success</h4>
        <p>{{ success | split('\n') | join('</p><p>') | raw }}</p>
    </div>
{% elseif error is defined %}
    <div class="error_box">
        <h4>Error</h4>
        <p>{{ error | split('\n') | join('</p><p>') | raw }}</p>
    </div>
{% endif %}