flectra/addons/website_mass_mailing/views/mass_mailing_view.xml

<?xml version="1.0" encoding="utf-8"?>
<flectra>
    <record model="ir.ui.view" id="view_mail_mass_mailing_list_form">
        <field name="name">mail.mass_mailing.list.form</field>
        <field name="model">mail.mass_mailing.list</field>
        <field name="inherit_id" ref="mass_mailing.view_mail_mass_mailing_list_form"/>
        <field name="arch" type="xml">
            <xpath expr="//sheet" position="inside">
                <notebook groups="website_mass_mailing.group_website_popup_on_exit">
                    <page string="Popup Content">
                        <field name="popup_content" widget="html_frame" options="{'editor_url': '/website_mass_mailing/field/popup_content'}"/>
                    </page>
                </notebook>
            </xpath>
            <xpath expr="//div[hasclass('oe_title')]" position="inside">
                <group groups="website_mass_mailing.group_website_popup_on_exit">
                    <field name="popup_redirect_url"/>
                </group>
            </xpath>
        </field>
    </record>
</flectra>