MyPost Carrier Printer Settings
Go to Settings > Carriers and click the blue cog to access the Printer Setup Page.
Basic Printer Settings
On this page you can view the available Label Formats for each of the label types; Standard, Express and International, each with set limitations of number per page depending on the label type.
If you intend to use a thermal printer, you need to set them to A6 - 1 per Page.
Note: It is a known issue with AusPost that international labels cannot be printed on an A6 label and they are reviewing their systems.