Earl Hicks, 66, of Cape Coral, Fla., was charged Monday in U.S. District Court with theft after the letters were found in a shed at an address in Algonac, Mich., where Hicks once lived, The Detroit News reported Tuesday.
The letters dated to the early 1990s and were to be delivered to postal stations in Oak Park and nearby Fenkell, a court affidavit said.
"Hicks stated that he was on a tight schedule and quite often would not begin his deliveries until after noon," the affidavit said.
Hicks allegedly told authorities he was afraid he would be fired if he returned the mail to the post office.
The overdue letters will be delivered once prosecutors approve their disposition, authorities said.