What does wtf mean on returned mail

A common question!

"WTF" on returned mail is an abbreviation for "Where's The Forwarding" or "Where's The Forwarding Address". It's a notation used by postal services to indicate that the mailpiece was returned to the sender because the recipient's address was incomplete, illegible, or non-existent.

In other words, the postal service couldn't deliver the mail because they didn't know where to send it. This can happen when the recipient has moved, is no longer at the address listed, or the address is incorrect.

When you see "WTF" on a returned mailpiece, it's usually accompanied by a reason code or a brief explanation of why the mail couldn't be delivered. This information can help you determine what went wrong and take corrective action, such as updating the recipient's address or sending the mail to a different location.