In most countries, mail insurance does not cover cash or jewelery. So even if you take out insurance, the post office is under no obligation to cover your losses if the money goes missing. Same for some of the courier companies, so be careful.
I avoid cash transactions. Paypal is so much easier.
But if I you have no other choice, here's what to do:
* Wrap your bills in aluminum foil - this has the affect of camouflaging the metal strip in most bills (overseas mail is often x-ray'ed and inspected automatically, so the metal strip are clearly visible) * Buy a box of chocolates in a tin, not cardboard box * Open the box very carefully * Place the cash under the chocolate in the box * carefully re-wrap
If you buy cheap, highly preserved, chocolate you can send your money by airmail. If you buy really good boutique chocolate, you'll have to send by express mail.
Either way, this gets expensive ... but you make many new friends.
Amir Avitzur R"G Israel
My chocolates come from ChocoNoy in Netanya (http://www.choconoy.co.il/)