As Maxcast discovered with his bank, my bank also offers a stop-payment on both certified checks and money orders with the burden of proof on the purchaser for the (legitimate) reason for stopping the payment. USPS offers no such service. Also, contrary to what has been said here, USPS does offer an International MO which can be purchased in US $ or the applicable currency at a current exchange rate. Cashiers checks and MO can be faked. I've not heard of a USPS money order ever being faked, though I'm sure it is possible...just not very likely. IMO, a USPS MO is the closest to getting cash in the mail, and the most secure form of payment. It is inexpensive and can be purchased in amounts up to $1000 using a bank debit card at any post office.
Marco
Marco