Hello! We're Atomic Returns, and we work with Canadian shippers through an account with EasyPost, Shipstation, or Shippo. We're free to install and test out and have been told we have the best features for the money. Some of our Canadian customers also require multiple languages and we support that too! Hope you give us a try.
You can check out the Multi Carrier Shipping Label app that allows you to generate return labels for all top carriers including Canada Post, DHL, UPS and many more. You can integrate your own Canada Post account, generate return labels for any of the orders, display the rates at checkout, print shipping labels and also automate shipment tracking. You can try the app with a 14-day free trial and contact the support for any assistance required.