How do I send messages to buddies who use .mac?
To start a conversation with a .mac user, tap the IMs button and then tap the new IM button in the upper right corner of the screen. Enter the user’s .mac address (e.g., example@mac.com) in the screen name field. You can also add .mac users to your Buddy List view by entering the name in the Add Buddy panel. You can also specify a nickname that will be displayed in lists instead of the user’s .mac name.