social/mail_reference/views/menus.xml

<odoo>

    <record id="action_view_mail_reference_mentions" model="ir.actions.act_window">
        <field name="name">Mail References</field>
        <field name="res_model">mail.reference.mention</field>
        <field name="view_type">form</field>
        <field name="view_mode">tree,form</field>
    </record>

    <menuitem
        name="Mail Reference Mentions"
        id="menu_mail_reference_mentions"
        parent="base.menu_email"
        sequence="99"
        action="action_view_mail_reference_mentions"/>

</odoo>