How do you unblock someone on mac i chat?

To unblock someone on Mac iChat, open the iChat application and go to the "Buddies" menu at the top of your screen. Select "Unblock Buddy" and then choose the person you want to unblock from the list. Alternatively, you can right-click on the blocked contact in your buddy list and select "Unblock" from the context menu. Once unblocked, you will be able to send and receive messages from that person again.