The only way letter mail is going to be singled out for extra attention is if a dog alerts to it and being in Australia with customs who have a hard on for bio security and anything else they can find canine detection is our biggest enemy. Any vendor shipping internationally should be using non permeable packaging as standard. I do agree with your earlier post though that it may not be a necessity for domestic, especially in your country where you have a plethora of vendors to choose from you lucky bastard!