What is true about undeliverable mail?

The statement that undeliverable mail is mail incorrectly addressed is correct. Undeliverable mail often arises from issues such as insufficient address details, incorrect postal codes, or outdated recipient information. When the postal service cannot determine where to deliver the mail due to these issues, it categorizes it as undeliverable.

In practice, undeliverable mail may not always be returned to the sender if the return address is missing or if the postal workers cannot ascertain the correct address. While postal employees may open mail under specific circumstances to determine the sender or recipient, the general rule protects the privacy of the mail. Additionally, undeliverable mail is not classified as lost property since it technically has not been misplaced but is rather caught in a delivery issue due to addressing problems.