social/mail_check_mailbox_size/data/cron_data.xml

<?xml version="1.0" encoding="utf-8"?>
<odoo>
    <data noupdate="1">
        <record id="ir_cron_check_mailbox_size" model="ir.cron">
            <field name="name">Check mailbox size</field>
            <field name="interval_number">1</field>
            <field name="interval_type">days</field>
            <field name="numbercall">-1</field>
            <field name="doall" eval="False"/>
            <field name="model_id" ref="fetchmail.model_fetchmail_server"/>
            <field name="code">model._check_mailboxes_size_cron()</field>
            <!-- Active flag is set on fetchmail_server.create/write -->
            <field name="active" eval="False"/>
        </record>
    </data>
</odoo>