If you have your contacts integrated with a phone, another low tech way to delete the duplicates is to delete them from your phone. That will sync over to the Outlook Lync folder and remove the duplicates.
Use Outlook Duplicates Remover Tool which is powerful and flexible plug-in for Microsoft Outlook intended for the search and processing of duplicates in Microsoft Outlook folders. It has ability to manually check everything that has been detected, in which you can cancel or remove the item.Read more: - http://www.mannatsoftware.com/stellar-phoenix-outlook-duplicate-remover.html
To remove your duplicate PST mailbox items quickly and easily by using Kernel for Outlook Duplicates Remover tool which is well works on all MS Outlook and Windows platform. User can get more information, visit to: http://www.free.outlookduplicateremover.org