Unclear how this AAI2 plot point worked out

Endgame spoilers for Turnabout for the Ages.

I was wondering about this part of Simeon's plan in which he acted as an intermediary for the correspondence chess between Kanis and Knight, which pretty much he only did it to implicate Knight as being Kanis' contact because they obviously check for inmates' mail and all that. I can totally see how Simeon can send anonymous letters to Kanis, but what I don't get is how Simeon can even receive any correspondence from Kanis every time since Simeon is supposed to be hidding.

Maybe this detail was explained in the game and it completely flew over my head. To be honest, this didn't take away from my enjoyment of this case or the game as a whole, but I wish I could understand this part a little better.