Fable
Those letters that never arrive must not keep being stuffed back into the mailbag
The mountain city post office had an automatic conveyor belt. Letters were placed on it, and sorting puppets delivered them to each street and each household by address. On most days, the mailbags came in in the morning and were empty by evening.
The trouble came from a few strange letters. Some addresses were missing lane names, some recipients had moved away, and some seals were damaged so the writing was illegible. The conveyor belt dumped undeliverable letters back at the entrance, the puppet tried again and again, and the whole belt was slowed down by a few bad letters.
The postmaster first made the puppet work harder: on failure, resend immediately, up to ten attempts. As a result, bad letters circled repeatedly at the entrance, and normal letters were blocked too. The second fix was to stuff failed letters into a corner of the desk, with no one logging them, and a few days later they were mistakenly dumped back into the bag.
The old postman proposed setting up a red box. Any letter that still fails after multiple retries, is missing key address fields, is refused by the recipient, or has a damaged cover leaves the main conveyor belt first, is dropped into the red box, and is tagged with the failure reason and last handling time.
The red box is not a trash can. A dedicated person checks it every day: those with fixable addresses get their addresses fixed, those that can be returned are returned, suspected fraud is handed to the street patrol, and those that cannot be handled are archived. The main conveyor belt therefore no longer gets stuck repeatedly on the same batch of bad letters.
Later, the mountain city post office actually became more reliable. The postmaster understood that failures should not be retried indefinitely, nor should they quietly disappear; undeliverable items need a separate queue, a recorded reason, and waiting for manual or special process handling.
The red box also exposed upstream problems. If letters from a certain street always ended up in the red box, it meant the address book needed updating; if a certain firm always sent damaged letters, the post office required it to change its envelopes. Once failures were seen in aggregate, it was not just about handling individual cases—the source could also be improved.
In the end, the postmaster set rules for the new puppets: retryable failures are retried by count, unrecoverable failures go into the red box, and every failure must carry a reason. Keep the main route clear, give anomalies somewhere to go, and the whole post office will not be dragged down by a few bad letters. Later, when new couriers started, their first lesson was not to fear failed letters. What is frightening is not that a letter cannot be delivered, but that it spins endlessly on the main route, holding up all the good letters, and no one knows why it failed. The clearer the red box, the more stable the main route, and the less normal mail is implicated. Later, the post office counted the red box every month, looking at both processing speed and which failures should be reduced at the source.