Thanks for the heads up Gregg, I use the AusPost email service quite often. I would report this to AusPost because they have an obligation to protect your privacy and it's very simple for them to do so (install SSL).
The AusPost tracking page (below) is not using HTTPS (secure HTTP), meaning scammers can eavesdrop on traffic between your web browser and the AusPost website. When you enter your email address and click "Subscribe", your email address is sent to the AusPost website and it is not encrypted. Anyone scanning the network will be able to read that information if they know what they're doing.
Track your item - Australia Post
General rule - if you don't see a padlock icon next to the URL or down the bottom of the page, any data you send to the website is open for attack.
If you're on a desktop you can always right-click inside the browser and select "view page info". Google Chrome will tell you "your connection to this site is not private".