From the AusPost website, see the penultimate para.:

Canada

Date: 27 November 2018
Expected delays: Ongoing

Canada Post continues to experience industrial action across Canada, which is causing significant delays in deliveries of letters and parcels to and from Canada. Canada Post has advised this is expected to continue for some time and have asked us to stop sending any parcels or letters to Canada.

All letters and parcels that were lodged with Australia Post on or before Monday 26 November will be sent to Canada on Tuesday 27 November for delivery.

We’ve also managed to find an alternative provider who will continue to accept International Express and International Courier products for delivery into Canada.

We are, however, unable to accept lodgements of letters or parcels for Standard or Economy services to Canada, from Tuesday 27 November 2018.

We appreciate this is not ideal. As soon as Canada Post advises us that they are able to accept lodgements again, we’ll recommence acceptance of all products to Canada – and will update this page accordingly.