A letter WorldVu sent by airmail and postmarked in Richmond, VA, on March 17 was returned as undeliverable on September 5. (Richmond, VA is 110 miles – 177 km. south of Washington, DC on the east coast of the U.S.)
The USPS and the Royal Mail handled the letter. Both of these postal operators handle millions of letters annually. Both are highly automated and (normally) efficient.
There is no indication of what the delay may have been in returning this undeliverable envelope. Why did it take so long? What caused this delay? Where was it delayed? I have no way of finding out the answers.
But this kind of delay has two lessons. (1) Unfortunately, we cannot depend on the international mails for timely deliveries and returns. We need to accept that some items will go missing or be delayed.
(2) Depending on returned items to eliminate undeliverable addresses or to correct addresses is not enough. Regular address data hygiene processing is needed to keep address files up-to-date.
A few days after the above envelope arrived, we received a domestic undeliverable return. A first-class letter to San Francisco, CA (on the west coast) came back in to us on the east coast in 3.5 months. This is an unusually long time for an undeliverable return through the USPS. I hope these two items are unusual occurrences and not an indication of a trend.