[chainsaw]

This one's a real mystery,

MY guess is the postal service. The OBL's unwilling partner.

[MizSterious]

If I heard correctly, they're checking her house, so if it came by mail, there should be some trace spores left behind. The lady in NY remains a mystery, because they found no anthrax anywhere in her house, where she works, or on the subway (how they can check that with any accuracy with so many people riding it, I don't know, just repeating what I read).