On June 16, 2011, Japan Post announced that they will stop accepting all postal services to Canada due to their strike starting on Friday, June 17, 2011 until the further notice.
Japan Post said they will anounce when they resume the service.
The letters and parcels that are already in route may get rejected and return to the senders. Japan Post will refund the postage if the sender claims it.
Press Release (Japanese)