odoo16/addons/mail/data/mail_templates_mailgateway.xml

<?xml version="1.0" encoding="utf-8"?>
<odoo>
    <data>
        <template id="message_notification_limit_email">
            <p>Dear Sender,</p>
            <p>
                The message below could not be accepted by the address <t t-esc="email"/> because you have
                contacted it too many times in the last few minutes.
                <br/>
                Please try again later.
            </p>
            <p>Kind Regards</p>
        </template>

        <template id="mail_bounce_catchall">
<div>
    <p>Hello <t t-esc="message['email_from']"/>,</p>
    <p>The email sent to <t t-esc="message['to']"/> cannot be processed. This address
    is used to collect replies and should not be used to directly contact <t t-esc="res_company.name"/>.</p>
    <p>Please contact us instead using <a t-att-href="'mailto:%s' % res_company.email"><t t-esc="res_company.email"/></a></p>
    <p>Regards,</p>
    <p>The <t t-esc="res_company.name"/> team.</p>
</div>
<blockquote><t t-esc="message['body']"/></blockquote>
        </template>

        <!-- Mail bounce alias mail template -->
        <template id="mail_bounce_alias_security">
<div><t t-out="body"/></div>
<blockquote><t t-out="message['body']"/></blockquote>
        </template>
    </data>
</odoo>