Just a reminder, THREE USPS facilities in South Florida were contaminated by anthrax. One was Boca Raton. Another was the West Palm Beach facility. Another was a special facility used to sequence mail to carrier routes.
Irrespective of the date of postmarks on any of the letters, none of them needed to pass through a canceling machine in order to get inserted into the postal mail processing system.
A letter carrier at the Staten Island post office was, in fact, arrested for involvement with the fellows who first tried to knock down the WTC with bombs.
Mail can "get lost" quite readily, particularly when it is single-piece rate First-Class letter mail! I provided detailed information concerning how letters mailed in Florida could get cancelled in New Jersey, and vice versa in numerous threads in FreeRepublic from November 2001 onward. If curious just search for "Anthrax".
I had proposed the letters were mailed on September 7 or 8, in Boca Raton, through the simple expedient of dropping them in letter mail collection boxes in the area. This family disappeared on 9/9. They had ample opportunity to mail the letters as proposed.
The handwriting on the anthrax envelopes might well match handwriting samples left around the house, as well. I wonder if the neighbors have any clue yet that anthrax is suspected to be in or around the house?
Thank you very, very much for the insightful details about mail processing. Could you answer a question about timing? AMA employees believed the letter with the odd powder arrived in their mail room about 9/8/01. Now the 8th was on a Saturday that year. So unless their mail room is open on a Saturday (quite possible considering the business they are in), it might actually have arrived during the week before or after the 8th. If the letter was mailed from a postal facility in South Florida close to the AMA building, how long would it likely take to be delivered? Obviously the answer to this question is important because of what happened on Tuesday, 9/11/01.