social/mail_digest/data/config_param.xml

<odoo>
    <data noupdate="1">
        <record id="mail_digest_enabled_message_types" model="ir.config_parameter">
            <field name="key">mail_digest.enabled_message_types</field>
            <!-- enabled by default for each message type -->
            <field name="value">email,notification,comment</field>
        </record>
    </data>
</odoo>