If you would like to synchronize/keep synchronized with MS Outlook, check to Enable Microsoft Outlook integration. If you don't intend to use MS Outlook integration, it is better to uncheck it. When unchecked, all the MS Outlook references and options will be hidden in the program.

Outlook will often require confirmation to ensure that access to email addresses is legitimate. If you cannot see the Outlook contacts appear, there is probably such an Outlook confirmation window waiting for confirmation.