I believe the FBI thesis is that the anthrax mailings were made just shortly before the discovery of people sick with anthrax, but after the 9/11 attack.
That's why they focus so closely on what Dr. Ivins was doing in the laboratory at night.
If, on the other hand the anthrax was acquired BEFORE the 9/11 attack, and was planned to be part of it, the spores could have been mailed in Florida (at Boca Raton in fact) as early as September 7 (Friday before the 9/11 attack).
The spore containing envelopes would have traveled by truck to Philadelphia as items later found to have been lost in the mail in surface transportation because all airlift capacity was grounded.
There were massive delays in processing mail for several weeks after 9/11. Most folks forget about that category of problems.
Iraq comes into the picture as a country well equipped to grow vast quantities of the Ft. Detrick spore sub-variety.
There are people in the FBI who do not want to implicate Iraq.
http://www.freerepublic.com/focus/news/2058705/posts?page=33#33
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