First off, the FBI was totally wrong on all of its advice and counsel regarding how the letters in question ended up in New Jersey. In some instances where it was impossible to explain how a "contaminated letter" got there, they threw up their hands in despair.
If they'd bothered to ask Postal Inspectors (who they hate for having demonstrated that Lon Horiuchi had no cause to fire at Ruby Ridge, and for many other things besides) they would have discovered that the mere fact a letter, or even a dozen letters, are cancelled in a specific facility, that's no reason to believe that the letters had to be entered into the mail at any serving post offices that may send mail to that facility.
The FBI could also have read FreeRepublic because I have covered this topic repeatedly. If they had done so they would have found that it is a trivial bit of analysis to discover that all of the letters were probably mailed at Boca Raton (where the AMI employee died), and were simply "lost" in a presumably empty flat tray, or trays, which were shipped from West Palm Beach P&DC to Philadelphia BMC and then out to Trenton, or a major mailer in the Trenton area (there are only 8 of them and not a single one of them has been reported to have been examined for anthrax contamination).
Once the anthrax letters were placed in a letter or flat tray, that tray itself became contaminated and could pass on the bacterial spores to anyone who handled the tray, or to any other mail placed in the tray.
It is more than likely the use of New Jersey references in the return addresses was serrendipitous than it was definitive regarding where the mail was entered and the route it traveled. In fact, my scenario - all the pieces entered in Boca Raton on or about September 8 - is really the only way you can account for the mail showing up at various times. A stack of "empty" flat trays would be worked down at a mailer's plant, and as each "lost letter" was discovered, it would be tossed into the mailer's own outgoing dispatch to the local post office. The trays, of course, would be refilled with mail at the mailer's plant.
Those trays might well have been used for different 5-digit sortations in the immediate Trenton vicinity. Although they didn't contain any anthrax laden letters, the bacteria would be "puffed out" through the polypropylene corrugations wherever the tray went and as it was used. There is a possibility that this action itself served to breakup the spore clumps into far smaller sizes.
Such a breakup would explain the "different qualities" of the anthrax mixture. As far as I know no one at the CDC has thought to "test the hypothesis". Of course, if they'd been reading FR 4 weeks ago they could have read about it right here.
There are more answers to all of the questions than are possible to put in this one thread.
Good point. And... which immigrants like to manage 7-11's and drive cabs (or do both, like that guy in Chicago)?
I think that someone from another country, who was used to writing the date as DD-MM-YY might chose to still write MM-DD-YY with a zero added at the beginning for months with 1 digit.
A question for the FBI: Why wouldn't an angry, native-born, lone scientist use a computer to write his note? If he were smart enough to imitate a medically-savvy Arabic letter writer he would be smart enough to know that Arabic letter writer would probably have a computer.
I think Atta wrote the notes and passed them to someone else to mail. He was angry and sweaty.