There is something people missed to fix up when a character is jailed. Altought you cannot read all letters by clicking on the character name on your family page, or can do it by bribbing the guards, and only a few of them, if you go through the messages menu, and, then, click on new messages, you can read all of them.
As it is antithetic, I can only think that the one who developed the code forgot to correct this.
