In Italy, I have had the following 4 experiences with Le Poste Italiane:
1) Birth certificate mailed certified mail with 1-week guaranteed service to New York City. Returned to sender with no explanation after two months. All address information was correct.
2) Two checks mailed certified mail with 1-week guaranteed service to a bank in Indiana. Delivered to the bank with no explanation after three months.
3) A legal document mailed certified mail with 24-hour guaranteed service to a court in Rome (three hours away). Never delivered.
4) Keys mailed certified mail with 3-day service from Ireland to Milan. Turned over to the Italian postal service after two days, and no sign of it since then. That was a week ago.
But we're the barbarians.