Koreen here from the Guru team at Shopify. Thanks for posting. :)
We do have a couple of Apps that can help you out here. I've included links below to those that facilitate an integration with TNT:
We also have our own Fulfilment API manual too. If this is something you'd like to implement independently, this should hopefully help to get you started. :)
You can check out the Shopify Shipment Tracking & Notify app. Once you have the TNT account credentials and API keys, the integration with TNT can be easily done in the app.
Once this is done, you will be able to automate your tracking process. The app automatically sends the tracking notification to your customers regarding the package. Also, you get an integrated tracking lookup page, by which your customers can track their product from your store.
Fei Song here from the Tracking More team. :)
Tracking More app will help you integrate tracking info from TNT.
1. Tracking More support TNT and other 645 couriers worldwide
2. Tracking More will send customized emails to buyers when shipping status changes( In transit, Out for delivery, Delivered, Failed attempt, Exception).
3. And you will get a tracking page.