Something else I didn't know:
A letter carrier handed Harry Wender an envelope from the U.S. Postal Service and asked for 40 cents "postage due" on it.
Harry thought that was strange. "Why should I pay 40 cents to get a letter from the Postal Service?" he asked.
The postman said he thought that inside the USPS envelope there was a letter that bore no stamp.
"Who's it from?" Harry asked. "Is it a piece of junk mail?"
"I don't know," the letter carrier said. "You have to open it to find out."
"And if I do open it . . . ?"
"That's right. If you open it, you have to pay."
The same thing happened to Olivia Klaben of Legal Secretaries, Inc. When I checked with the Postal Service, I was told that if letters without stamps bear return addresses, they are returned to the sender. If not, they go to the dead letter office, which charges 40 cents for trying to find out to whom to return the letter. If there's no clue, the letter is forwarded, postage due. If you open the envelope to see who sent you an unstamped letter, you're stuck.