Not often I comment on the boards but here is some basics.

We lodge all items over the counter at Aust Post and keep a record of all items sent in excel.  We get Aust Post to verify our records by stamping every day.  This provides some paperwork in the case of chargebacks.

Next if a customer complains about non delivery re send to thier local post office NOT to the same address that you sent goods to.  We have found over the 15 years that many of the people who complain have not got the full or correct address on eBay and then blame the seller.

All Aust Post offices will hold mail (eg John Smith c\- Anytown Local Post Office).  The big trick her is to get the buyer to understand that it is not registered and they need to go into the local post office and state the item is being held c/- local post office.  ( Many travellers use this method of receiving mail)

Australia Post has also introduced tracking labels for all parcels which is great apart from the fact that many sellers like to get postage costs down and use letter/ large letter rates.

If you find a pattern of a person not receiving goods then put it on feedback so other sellers, eBay and PayPal can see the buyer is not getting items.

Australia Post will investigate an area if a pattern arises.

Hope this helps a little