Assume that you have multiple contacts who have the same work number in the Contacts view in Microsoft Outlook 2010. Then, you sign in to a Microsoft Lync 2010 client that has the Lync Online service enabled. In this situation, the contacts who have the same work telephone number in your Outlook Contacts view may be displayed with incorrect contact information in the Lync 2010 client, such as an incorrect contact name or an incorrect email address.
This issue also occurs:
If you search for one of the contacts in the Lync 2010 client, the search result may display the information of a different contact who has the same work number in your Outlook Contacts view.
If you start a conversation with one of the contacts, the information of the contact may be displayed incorrectly in the conversation window.
If you receive a toast notification from one of the contacts, the information of the contact may be displayed incorrectly in the notification.
To resolve this issue, install the following cumulative update:
2912208 Description of the cumulative update package for Lync 2010: January 2014
To apply this update, you must create the DisableReverseNumberLookup registry subkey in the following location, and set the value of this registry subkey to 1:HKEY_LOCAL_MACHINE\SOFTWARE\Policies\Microsoft\Communicator