My name is ***** ***** I am a NSW Solicitor. Thank you for your question, and will do my best to assist you with your question. Please understand this is not legal advise but a guide to assist you.
They cannot open your mail it is a breach of the postal act.
It is tampering with mail
Here is some information.
You can report it to Australia post or the police. I am not sure they will do much but you cannot sue civilly for this as it is a criminal offence.
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