They sell them! Seriously! Packages or bundles of multiple packages are typically auctioned off when they have been labeled as "Undeliverable" for a certain amount of time, 30-60 days I presume. Personally, I believe they sabotage any and all items they can so they won't have to deal with it & packages are intentionally marked "undeliverable" when the mail carrier is either too stupid or too lazy to get it in the recipient hands. That is my opinion that I formed from too much pointless research on USPS. BUT, The packages are really auctioned off! That is a fact, not my personal opinion.