several ways. One is to send the item Certified Mail. Another would be Registered Mail (think it's still available). And a third is a less costly Proof of Delivery involving filling out a small slip of paper and giving it to the Postal Clerk - it used to cost 40¢ but I am sure it is higher now. These will show when the letter was delivered. The Tracking Feature is a more detailed, and sometimes fun, method - you can find your package went from the local post office to some Sectional Facility Center, then sent out on a truck to another Center in, say, Kankakee by mistake, then mistake noted, then it goes on to Chicago, ooops that's not right either, then it goes hopscotching across the country. . . blah blah blah, eventually to the recipient just up the street from you where it was supposed to go directly. Lest I offend the USPS let me add that such mishaps are uncommon. But it has happened to at least one very tired package I sent out.