With the update complete, Microsoft has updated Xbox.com with a new feature called "My Xbox Message Center".
# All My Xbox users (Xbox Live Silver and Gold users as well as those who just signed up here on Xbox.com) can now read text messages in the My Xbox Message Center. So someone can send you a message from their Xbox 360 console and you can read it on your PC.
# Xbox Live Gold members can compose and send messages in the My Xbox Message Center. The character limit is the same as on the Xbox 360 console: 250 characters.
# Xbox Live Gold members can send messages (up to 200 per day) to gamers who are on their friends list.
# Xbox Live Gold members can send messages (up to 25 per day) to other gamers not on their friends list.
# All My Xbox users can block communications with other gamers. Designate a gamertag as blocked and you won't get any more messages from them. Change your mind?
# Unblock a gamer simply by sending them a message.