Administration of Active Directory does not have to be hard. Too often what should be a simple task is made more difficult than it needs to be.The solution? Hyena from SystemTools Software. With ease-of-use as well as powerful importing and bulk updating capabilities.
See the note under "What do you need to know before you begin?" here: https://technet.microsoft.com/en-us/library/bb691354(v=exchg.160).aspx