[Eroteme]

There’s no conceivable reason for them not to drop the letters in a mailbox at Logan or Dulles or whatever on their way to board the planes,

Perhaps. But you're applying standard, western logic to analyze the strategy/tactics of unknown individuals who may operate under quite different reasoning processes.

I hold no strong opinion on who the likely culprits might be. But I rule out none, either, based solely on what "makes sense" to me.

[muawiyah]

Several of the terrorists spent time in Boca Raton FL before departing from there to make their attack.

One of the dead guys killed by anthrax was in that area.

Never forget that ~ the thesis that begins at Boca Raton has in it a very clear trail of death. All the other theses, as well crafted as they might be, have a stumbling block in the killing in Florida.