No I don't believe it's coincidental.
If an unassociated group of right wing crazies started sending out Anthrax on September 9th, then it would just be a big old coincidence.
Not really that big or that old. From subsequent news reports, specials, and documentaries it seems more than a few people knew that something big was gonna happen with nearly a 100% guarantee. It's just that no one knew what. My point is that it's not coincidental if the anthrax-people, whoever they are, had prior knowledge of the attack (even without the specifics).
Now about that bridge you want to sell me ... :)
Why would the right wing crazies be sending Anthrax to Nairobi, Kenya a few days before the Muslim crazies blew up skyscrapers and started sending Anthrax all over the US? The right wing crazies have never done anything in Kenya. They probably could not even find Kenya on a map. The Muslim crazies, on the other hand, have blown up an American Embassy in Nairobi, Kenya, and one in Tanzania, too.
And yet you persist in suggesting that the September 9 mailing to Kenya was the work of right wing crazies. Why? What possible motivation would they have?