I have found that during my years with ebay as a seller of collectables and sometimes rare items - that honesty is indeed the right policy in all aspects of your business.

Say for instance - you no longer have the item for sale - someone has purchased an item out of your ebay shop or auction and for whatever reason - you no longer have the item - or the item is not as in good condition as stated -  BE HONEST WITH YOUR CUSTOMER - don't try and fob them of with excuses - because the customer always knows when they are being led and lied to. 

At least if you are honest with them - yes they might be disappointed or even angry - but most people have an understanding mind and you will have a chance to explain yourself. 

You might have inadvertedly listed something twice (it happens!!) and you only have one in stock or what you listed 2 months ago was mint at the time, but is no longer because it has got damaged in some way - CONTACT YOUR BUYER BEFORE SENDING OFF - i have only learnt these lessons by making mistakes myself. 

This way you can avoid disappointed, angry customers (most of the time!!) and avoid negative feedback which could end up damaging your reputation and this is one of the hardest aspect of the business to learn is reputation - because this is the first thing a customer will look for before buying of you.

I hope this guide has helped you in some way and you can avoid some of the problems which arise through lack of being completely honest with your customers/buyers - either internationally or otherwise.