I can't answer the email/turn chess technical question, but as for standard OTB (over the board) rules...
If an illegal move has been made and neither player has noticed it for at least 10 moves afterwards, then the game continues on as played. If it is discovered within 10 moves, then you must return to the position where the error occured and play a legal move. Touch move still applies, so having touched the king you'd now have to move it if possible.
Correct me ifI am wrong; a king having been checked, but the check was blocked by another piece, can still castle. A king can not castle out of check nor across check. Either on line or OTB.
Correct me ifI am wrong; a king having been checked, but the check was blocked by another piece, can still castle. A king can not castle out of check nor across check. Either on line or OTB.
Yes, you lose castling rights permanently for having moved the King (or the Rook that you intend to use) and cannot castle out of, through, or into check - though it makes no difference if the Rook is attacked or moves through a controlled square.
IIRC Korchnoi, no less, once asked a tournament controller if he could castle when the Rook was attacked, explaining "it's never come up before".
I have on this site seen that happen. I attacked the guy's rook and he castled much to my surprise.
When playing the computer it won't let you castle after having been in check, but I notice this is not the same when playing email chess. Castling will be accepted even if you have been in check - should this be fixed?
Also, what are the rules if you castle having been in check? If your opponent doesn't notice until several moves later do you play on?