The error (Shipment API Error:553The sender address postcode does not have the minimum length539The collection postcode is below the minimum length) from TNT is caused by the Warehouse Postcode not having the correct information in it, please make sure the Postcode is entered correctly within the Warehouse Address.
To resolve this, please follow the steps below:
Click Warehouse the Manage Warehouses.
Find the warehouse.
Click Edit and check the Post Code field within the warehouse address details.
Finally, click Update and retry the shipment.