IMO, legally your domestic mail has more privacy rights than international shipments. When you order, make sure your source is protecting you. Are they using encrypted mail? Will they send delivery confirmation but not signature required? True, controlled deliveries require you take possession, but there is a difference between taking possession of just the one package from a PO box that nothing else gets mailed to and taking possession as incident by retrieving all your mail from the box and this package just happened to be in with your mail. It could later be argued that you were simply retrieving your mail and didnt scrutinize the "package" and therefore was not aware of "it". Dont think these are not mitigating factors. Any good attorney will tell you that first he must challenge the validity of the charge, the legality of the warrant and the issuance of rights, then he must attack the evidence to supress what he can, then he must attack any testimoney given to strike or rebut what he can, then of what remains he must mitigate and mitigate and mitigate, then file a string of objections just in case of conviction to give a possibility for remand upon appeal. Dont ever by big, if you exceed a certain quantity, you step up to with intent to distribute and the penalty is much greater. Buy within the personal use guidline for your state, buy domestically, no signature, to your house is fine, just not often, and I would always leave anything suspicious I found in my mail laying outside for a while just for good measure.
