they also used the anthrax attacks as an excuse to ramp up the tracking of letters
the reason it takes more than one day to deliver a letter now
there are no "local" letters now, they all go to larger sorting centers and every letter is photographed front and back
they even push this as a benefit called
usps informed delivery service
see your mail before it arrives
of course if anyone is interested and has access to the data
they could type in your name and address and see every letter you have ever sent or received
but surely no one would do that