Customs don't check domestic post. Overseas only. When the customs check they are still not allowed to open the parcel unless the owner is there with them. That is why if your stuff got held you or your appointed agent has to go clear with the customs need to open the parcel in front of them and show them what the item you bought. That's the real procedure which was told to me by a custom officer there.

Yes...and it irked me more when they stupidly say why cannot buy here when I show them what I buy? Duh! If I can I would not bother to get from overseas if what I want can be bought here!! Either they are stupid or just like to see us suffer