DHL tracking IDs or shipment IDs are deleted at different times depending on the service and the business unit. In general, most are purged after 90 days once the shipment has been delivered; or a long time has passed from the last event.
Only some tracking IDs are stored and displayed for up to a year. For the best use of our systems, we ask that you stop tracking any shipment once it has been delivered.
If you try to track a shipment with a purged tracking ID, the API will return either a 404 or 500 error, depending on how fast it identifies it's an invalid tracking ID. Both error messages are correct and expected. You are more likely to get a 500 error for a purged tracking ID, as well as more likely to get a 404 error for an incorrect tracking ID that has a composition not related to our detection logic.