1. First u should know how offline address books works 

  2. Then u should know how outlook to download offline address books 

  3. The Last is how to troubleshoot that outlook download OAB failed 



http://careexchange.in/how-offline-address-books-works-in-exchange-2010/


http://www.howto-outlook.com/howto/oabupdate.htm


https://blogs.technet.microsoft.com/rmilne/2012/08/10/outlook-fails-to-download-oab/