Mino – The UC Guy

Microsoft Unified Communications Blog

Communicator error ” Cannot Synchronize Address Book “

Posted by Mino on November 17, 2008

A common issue we see is clients getting an error stating “Cannot Synchronize Address Book”.  It looks like this:





This is an action that the OCS installation doesn’t take care of automatically so it happens pretty regularly.  To resolve it, select the Directory Security tab and click on the Server Certificate Button


After you click on the Server Certificate button, follow the Wizard, select Assign an Existing Certificate and assign the certificate used by your OCS Server for client logins.  Once you’ve assigned the certificate the SSL port on the Web Site tab should be filled in with port 443. 

Sign your clients out of Communicator and then back in and the Address Book should be downloaded successfully


PS : if you are using Exchange 2007 Selfsigned Certificate , you should also recieve this error still and that it because the self signed certificate for exchange is not trusted by OCS 2007 . so you should either replace the exchange 2007 self signed certificate with a certificate from the same CA as the OCS 2007 or you should import the exchange self signed certificate inside the OCS 2007 servers in the Trust Certificate store  

One Response to “Communicator error ” Cannot Synchronize Address Book “”

  1. Ian Salgado said


    How do you correct this same error in Lync 2010 & Lync Client 2010 ?

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