[Nogbad]

I have long believed the anthrax was aerosolized overseas and brought here.

Yes, and probably the envelopes were filled overseas as well.
But I have long speculated that some extra lower-grade anthrax was provided
to the hijackers to play around with
so that they wouldn't be tempted to open the envelopes
and use the high-grade stuff in some other way.

[Alamo-Girl]

Thanks for the heads up!