What I’m saying that sending money with the Postal Money Order (there is something like it even in Italy), will let everyone knows that you are sending an amount of money to someone else, so because of this it is a traceable money transfer.
Instead using the assured mail without saying to anyone that you are sending cash money, it will be different and it will not be a traceable money transfer. 
this type of method would work in Canada for certified money orders
A customer wishing to determine the status of their Money Order(s) when
the payee claims it was not received or the sender claims to have
misplaced or lost the Money Order will need to call the Money Order
Verification Service (MOVS) at 1-800-563-0444.
reference - https://www.canadapost.ca/tools/pg/manual/PGmoneyord-e.asp
Sorry, we really don’t support ‘horse and buggy’ technologies like PMO or cheques unless it’s the only option for that region.
You could use a Banker’s Cheque - a bank-to-bank transfer. If it’s encashed, there will be a record of the transfer on your bank’s website (online account statement) and if the draft was cancelled, there will be a record of that as well. I’m not sure that someone can hold a draft indefinitely so interesting question for the bankers. Anyway to prove you had created such a draft, the only sure way would be to allow moderator access to your account. This can be quite safe, banks allow read access to online banking. However none of the usual exchanges accept a foreign currency demand draft.
One other thing, you may be able to forge a FCDD but short of that - it’s a bank bank transaction, and you can’t endorse it to someone else. If it is encashed legally, the money will go to the target account only. It’s an order to the destination bank sent through post…
All this is horribly inconvenient 
but cheap and possible (barring the forgery thing)