Evidence of his involvement is less than overwhelming.
A very limited circulation periodical subscribed to by Ivins wife contained an article on mailing to the two senators and the newscaster using addresses in exactly that format.
Do not confound evidence implicating that laboratory, and that source of address information, with IVINS himself.
Quite frankly I think this was an amateurish attempt to frame IVINS carried out by one of the attackers' sympathizers who worked in the same laboratory with IVINS. He not only stole anthrax he stole that publication.
The envelopes were mailed in Boca Raton ~ mishandled due to their placement after hours in a specific sized mail tray used in a post office mail collection boxes. That tray was then sent to the mail equipment distribution site in Eastern Pennsylvania, and in turn sent over to a customer site served by the Franklin township facility ~ where they were all finally postmarked.
By ignorning my very detailed information regarding mail flow on the East Coast the FBI BLEW THE CASE and arrived 7 years to late to the proximity of the theft of some of the anthrax used in the attack.