As a retired Mailman, Can tell you I used to get all sorts of missent letter, parcels, etc. A lot has to do with the ability to read the address,
especially Zip Codes. Machines do a lot of sorting at the plants. And barcoding.
I worked in NJ, I would get letters from 1 part of Houston to the other,
via NJ. Due to stupid, so called "More efficient" machines.
<S> Oz