Well I can not give you more proof of how much incoming international mail is screened in Australia than documents from Australian customs, the contractors they have hired to be able to screen the amount of mail they claim to, quotes from Australian customs officials, and my own personal conversations and interactions with Australians (who in my experience tend to have far more interceptions than people in other countries). Maybe you have managed to get more than an envelope through, I have no idea and I don't really give a shit, consider yourself lucky. All I know is if I spend the time to hunt down articles and .pdfs that I can give a dozen citations of claims of Australia inspecting 100% of incoming international mail (and one report that said 100% of international mail other than letters). I am not sure if I feel like digging up all of these old things I have read though, as I already gave a link to one .pdf as a citation and that is more than anyone has been able to show to the contrary other than anecdotal evidence from you.