'Get specific notification email values to store on the notification
mail_mail. Void method, inherit it to add custom values.'

@api.multi
def message_get_email_values(self, notif_mail=None):

    self.ensure_one()
    database_uuid = self.env['ir.config_parameter'].get_param('database.uuid')
    return {'headers': repr({'X-Odoo-Objects': ('%s-%s' % (self._name, self.id)), 'X-Odoo-db-uuid': database_uuid})}
