Postal spokesman Ed Moore said the case is a "black eye" for carriers who faithfully deliver mail.
"The sanctity of the mail is important to us and the American public," he said.
In a 1996 "Seinfeld" episode, Newman (Wayne Knight) stored mail in Jerry Seinfeld's storage unit instead of delivering it.
Hull worked for the Postal Service for 3 1/2 years, filling in for other carriers in the Howell area, about 60 miles northwest of Detroit.
"Hull said she was unable to get the mail delivered on time, so she left what she could not deliver in her car and drove around with it," postal agent Douglas Mills wrote.
"She said after a couple of weeks of doing this, she realized that nobody seemed to notice that she did not deliver it. ... At that point she knew she had to get rid of the undelivered mail," Mills said in an affidavit to support a theft charge filed in federal court in Detroit.
Hull made payments on the storage unit from January 2006 through November 2007.
She had hoped to catch up on her overdue payments and then continue to rent the space "until the day I died," Mills quoted her as saying.
Hull quit her job in August, about three weeks before the mail was discovered.
Hull could not be reached for comment. A phone number listed for her was disconnected.
Because the mail is evidence in a criminal case, it's not known when it finally will be delivered.
"It could take some time," said Breck Nowlin, a senior agent with the Postal Service's Office of Inspector General. "Our agents have looked through the mail. Where they have found birthday cards, greeting cards, they took the time to locate some of the people and let them know it will be delivered."
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