they used the anthrax "attack" as the excuse to start tracking every letter mailed in the us
i am sure it had already started in the major cities
most of the people that died worked in a huge mail sorting building, except one elderly woman
the speculation was the anthrax had rubbed off on a letter she recieved
at the time (2001) i am sure that i heard someone from the post office say that they had checked the 500 letters that went through the machine before and after the suspect letter
this was a week or 2 later and i thought at the time
how can you check the letters from the
past unless you are keeping track of them all
never heard it mentioned again
15 years later they admit they track all letters
that is why there are no "local" drop boxes anymore
all letters must go to a large enough place that has sorters with cameras
photos front and back