- Open Messages Preferences from the Messages menu.
- Click the Accounts tab and choose the account in which you want to apply privacy settings.
- Click the Privacy tab (if available) within that chosen account to see the settings.
To proactively determine who can see that you’re online and send you messages, choose a privacy level that you’re comfortable with. The options are
- Allow anyone.
- Allow people in my buddy list.
- Allow specific people. (If you make this choice, you have to type each person’s AIM, .mac.com, iCloud.com, or .me.com address.)
- Block everyone.
- Block specific people. (Again, type the appropriate addresses.)
You can also arrange, inside Messages Preferences, to receive a notification whenever you get a message from unknown contacts. Or get a notification when your name is mentioned. Select the appropriate check boxes on the General tab to select these options.
Sometimes you’ll want to take leave of a particular conversation, at least temporarily. If so, click the Details button, and select the Do Not Disturb check box to mute notifications for the given conversation.