odoo16/addons/mail_group/data/mail_template_data.xml

<?xml version="1.0" encoding="utf-8"?>
<odoo>
    <record id="mail_template_guidelines" model="mail.template">
        <field name="name">Mail Group: Send Guidelines</field>
        <field name="model_id" ref="mail_group.model_mail_group_member"/>
        <field name="subject">Guidelines of group {{ object.mail_group_id.name }}</field>
        <field name="email_to">{{ object.email }}</field>
        <field name="description">Sent to people who subscribed to a mailing group with group guidelines</field>
        <field name="body_html" type="html">
            <div>
                <p>Hello <t t-out="object.partner_id.name or ''"></t>,</p>
                <p>Please find below the guidelines of the {{ object.mail_group_id.name }} mailing list.</p>
                <p><t t-out="object.mail_group_id.moderation_guidelines_msg or ''"></t></p>
            </div>
        </field>
        <field name="lang">{{ object.partner_id.lang }}</field>
        <field name="auto_delete" eval="True"/>
    </record>

    <!-- Confirm subscription email -->
    <record id="mail_template_list_subscribe" model="mail.template">
        <field name="name">Mail Group: Mailing List Subscription</field>
        <field name="model_id" ref="mail_group.model_mail_group"/>
        <field name="subject">Confirm subscription to {{ object.name }}</field>
        <field name="description">Subscription confirmation to a mailing group</field>
        <field name="body_html" type="html">
            <div style="margin: 0px; padding: 0px;">
                Hello,<br/><br/>
                You have requested to be subscribed to the mailing list <strong t-out="object.name or ''"></strong>.
                <br/><br/>
                To confirm, please visit the following link: <strong t-if="ctx.get('token_url')"><a t-att-href="ctx['token_url']"><t t-out="ctx['token_url'] or ''"></t></a></strong>
                <br/><br/>
                If this was a mistake or you did not requested this action, please ignore this message.
            </div>
        </field>
        <field name="auto_delete" eval="True"/>
    </record>

    <!-- Confirm unsubscription email -->
    <record id="mail_template_list_unsubscribe" model="mail.template">
        <field name="name">Mail Group: Mailing List Unsubscription</field>
        <field name="model_id" ref="mail_group.model_mail_group"/>
        <field name="subject">Confirm unsubscription to {{ object.name }}</field>
        <field name="description">Sent to people who unsubscribed from a mailing group</field>
        <field name="body_html" type="html">
            <div style="margin: 0px; padding: 0px;">
                Hello,<br/><br/>
                You have requested to be unsubscribed to the mailing list <strong t-out="object.name or ''"></strong>.
                <br/><br/>
                To confirm, please visit the following link: <strong t-if="ctx.get('token_url')"><a t-att-href="ctx['token_url']"><t t-out="ctx['token_url'] or ''"></t></a></strong>.
                <br/><br/>
                If this was a mistake or you did not requested this action, please ignore this message.
            </div>
        </field>
        <field name="auto_delete" eval="True"/>
    </record>
</odoo>