Of course this is nonsense. The THIS IS NEXT was from the Sept 18 letter that most recipients just threw in the garbage. No one knew what the idiot was taking about. He was so delusional that he sent a letter about anthrax and never included the word anthrax! The guy was a complete moron. When the victims developed lesions, they thought they were insect bites!
Our clueless clown then wrote the second letter, which included WE HAVE THIS ANTHRAX, YOU CAN NOT STOP US, expecting people to believe that the letters came from the dead hijackers. Utter nonsense that was believed by a few nuts into involved convolted plots involving "sleeper cells".
If you think about, these detailed plans designed to deceive were somewhat like the attempted "perfect crime" of Leonard and Loeb who created the fake names of Morton P Ballard and Louis Mason and left clues to shift the blame elsewhere. Now what moron(s) would immitate those clowns, who messed up big time and got life plus 99 years for ONE murder.
The anthrax mailer(s) should be so lucky!