By default, Outlook highlights unread messages in your Inbox with a bold font. You can change this to use a color, a bigger font, or even a completely different font.

To change the way unread mail is highlighted in Outlook:

1. Select View | Arrange By | Current View | Customize Current View from the menu while you are in your Outlook Inbox.
2. Click on Automatic Formatting.
3. Select Unread Messages.
4. Click on Font....
5. Specify your desired settings.
6. Click OK.