Odoo-Build/snippets/mail.mail_notification_paynow.replace_footer.xml

<data inherit_id="mail.mail_notification_paynow" priority="50">
    <xpath expr="//tbody/tr[3]/td/div" position="replace">
        <div style="color: #999999">
            <a t-att-href="'%s' % company.website" style="text-decoration:none; color: #999999;">
                example.ch
            </a>
        </div>
    </xpath>
</data>