mail-addons/mailgun/data/ir_cron_data.xml

<?xml version="1.0" encoding="utf-8"?>
<openerp>
  <data noupdate="1">
    <record id="mailgun_domain_verification" model="ir.cron">
      <field name="name">Mailgun - domain verification request</field>
      <field name="model_id" ref="model_ir_config_parameter"/>
      <field name="interval_number">10</field>
      <field name="interval_type">minutes</field>
      <field name="numbercall">10</field>
      <field name="state">code</field>
      <field name="code">model.mailgun_verify()</field>
      <field name="doall" eval="True"/>
    </record>
  </data>
</openerp>