At least with the USPS stringent signature requirements with registered mail there are enough bread crumbs to find where it breaks down. Son' s FIL is a retired postal inspector having had a second career after a career in the USN. Finding rotten eggs in the system was his job. One less than elegant method was the mailing of silver dollars that could be easily felt in envelopes. After each stage of "handling" they were able to isolate where the theft occurred. Some folks can resist everything but temptation. Gil