odoo 9 run to error on incoming mail processing

2015-10-21 16:37:49,722 14422 INFO db90 openerp.addons.fetchmail.fetchmail: Failed to process mail from pop server e-mails.
Traceback (most recent call last):
  File "/odoo9/local/lib/python2.7/site-packages/odoo-9.0-py2.7.egg/openerp/addons/fetchmail/fetchmail.py", line 225, in fetch_mail
    context=context)
  File "/odoo9/local/lib/python2.7/site-packages/odoo-9.0-py2.7.egg/openerp/api.py", line 223, in wrapper
    return old_api(self, *args, **kwargs)
  File "/odoo9/local/lib/python2.7/site-packages/odoo-9.0-py2.7.egg/openerp/api.py", line 318, in old_api
    result = method(recs, *args, **kwargs)
  File "/odoo9/local/lib/python2.7/site-packages/odoo-9.0-py2.7.egg/openerp/addons/mail/models/mail_thread.py", line 1155, in message_process
    routes = self.message_route(msg_txt, msg, model, thread_id, custom_values)
  File "/odoo9/local/lib/python2.7/site-packages/odoo-9.0-py2.7.egg/openerp/api.py", line 221, in wrapper
    return new_api(self, *args, **kwargs)
  File "/odoo9/local/lib/python2.7/site-packages/odoo-9.0-py2.7.egg/openerp/addons/mail/models/mail_thread.py", line 1045, in message_route
    update_author=True, assert_model=True)
  File "/odoo9/local/lib/python2.7/site-packages/odoo-9.0-py2.7.egg/openerp/api.py", line 221, in wrapper
    return new_api(self, *args, **kwargs)
  File "/odoo9/local/lib/python2.7/site-packages/odoo-9.0-py2.7.egg/openerp/addons/mail/models/mail_thread.py", line 796, in message_route_verify
    raise ValueError('Routing: posting a message without model should be with a parent_id (private mesage).')
ValueError: Routing: posting a message without model should be with a parent_id (private mesage).