how did they know

[grizzbass]

Several years ago, I used to mail Christmas cards. (I've dropped out of the practice over the years for various reasons.) Back then, I found it odd that of the cards that I mailed the same day, the ones that went outside my hometown only took 2-3 days to arrive at their destinations, while the ones that had addresses within my own ZIP code took over a week!

Similarly, I have received cards from people outside my current city of residence 2-3 days before cards postmarked the same day sent by people living less than 5 miles from me (and presumably processed at the local post office branch).

if you mail a letter to someone in the city they send it to Salt Lake City first. Then they send it back. That has been the proceedure since