I thoroughly enjoyed this story, but wonder if the details have changed a bit over time, perhaps? If light can travel ~558 miles in 3 milliseconds, it seems tha

I thoroughly enjoyed this story, but wonder if the details have changed a bit over time, perhaps? If light can travel ~558 miles in 3 milliseconds, it seems that mail sent more than 250 miles would have failed (because RTT)? Also, I'm not sure how big a difference it makes, but signals propagate at less than the "speed of light" (vacuum) when the medium is copper.