But now I want to tackle the Iranian question more directly. While the appearance of anthrax is suggestive of Iraq (post #175), as Mitchell points out (post #147), the rhetoric in the letters is characteristic of Iran. "Death to America, death to Israel" - those are Hezbollah slogans.
A week after 9/11, janes.com floated the theory, attributed to Israeli military intelligence, that it was the work of Iraq, acting through Hezbollah's Imad Mughniyeh and al Qaeda's Ayman al-Zawahiri. (The report prompted a response in the Jerusalem Post a few days later - "IDF: Iraq Not Involved in Attacks, Iran Maybe".) Curiously, there is a document out there, purporting to be a memo from Iran's supreme leader Ali Khamenei to the senior official Ali Akbar Nateq-Nouri, saying that Iran should expand its secret cooperation with Mughniyeh and Zawahiri, in preparation for attacks on the USA. The document was apparently supplied by Hamid Reza Zakeri, an Iranian defector.
In the letters, then, we have something suggestive of Iraq, and something suggestive of Iran; and we even have two theories which agree that 9/11 was the work of Mughniyeh and Zawahiri, but disagree on whether the state sponsor was Iraq or Iran.
So once again we have several possibilities. It could be Iraq trying to make it look like Iran, or Iran trying to make it look like Iraq. It could be Iraq or Iran acting without the intention to frame the other. It could be both Iran and Iraq. It could be neither Iran nor Iraq.
Luigi Warren pointed out to me that Iraq would appear to have a much stronger motive than Iran. Iraq was engaged in a ten-year hot and cold war with the USA which involved punishing sanctions and regular bombardment. The US campaign against Iran during that period, if such a thing existed at all, was tepid by comparison. However, this lack of pragmatic motivation has to be weighed against Iran's anti-American ideology ("death to America", remember).
Somewhere in Bob Woodward's Bush at War, George Tenet says he thinks that investigators will discover that Iranian and Iraqi "mood music" surrounded the 9/11 plot. J.K. Idema, the former Green Beret who was recently arrested in Afghanistan for his counterterrorist freelancing, said as much in his interviews.
According to Laurie Mylroie's Study of Revenge, Wafiq al-Samarrai, Iraq's former chief of military intelligence, said that Saddam hoped to attack the USA and make it look like the work of Iran. Meanwhile, former intelligence officials Patrick Lang and Larry Johnson have promoted the idea that INC leader Ahmed Chalabi is an Iranian agent fabricating evidence about Iraq's WMD programs and terrorist connections. Both Iraq and Iran were active in Sudan while al Qaeda was hosted there...
So, at least superficially, you can make a case for any of the possibilities I listed. How does this relate to the anthrax letters? Well, I am assuming that they were part of the 9/11 plot, and these possibilities all correspond to different theories of the mechanisms and intentions behind 9/11. If the anthrax letters are part of the plot as well, we have to find room for them in the story of 9/11's genesis, planning, and execution. Or rather, 9/11 itself becomes a subplot in a larger, as yet untold story, "9/11 + Anthrax".