One of my favorite unheralded Mavericks features is the ability to control whether or not previews appear when you get notifications. As you know, this is what a typical email notification might look like:
That’s great and all, but what if you don’t want that much information to show up randomly on your machine? It certainly wouldn’t be ideal to get an embarrassing email while your boss happened to be standing behind you. Of course, we can turn notifications off entirely, but I think it's awfully nice to know who has sent me something when it happens. Mavericks to the rescue! So to play around with this new privacy feature, visit System Preferences> Notifications, click on a category that supports showing previews (such as Mail or Messages), and then check out the options you’ve got with the "Show message preview" setting.
There are three choices here. First, you can toggle off previews entirely, which’ll mean you’ll get notifications like this one, showing who has sent you a message but not the subject or any content within it:
With “Show message preview” turned on, though, you still have some control over what happens. Click on the drop-down menu next to it, and you can pick between “always” and “when unlocked.”
Obviously, the “always” choice does what it says; previews for your messages will show up regardless of whether your machine is displaying your screen saver, for example. But if you change that to “when unlocked,” people won’t be able to walk by when you’re not there and tell what kind of emails you’re receiving. Hey, just because you're paranoid doesn’t mean that they’re not out to get you, right?