Lync Address Book – Client Synchronization Errors and Common Problems

Address Book synchronization issues are common with new Lync deployments. Issues usually surface as errors in the Lync client shortly after sign-in (when the address book synchronization is first attempted) and manifest as one of these two errors:

Lync Address Book Issue

Or, shortly after upgrading from the Communicator client, users will see the following error beneath the contact search text box:

Lync Client Synchronization Error

Some address book issues are caused by a problem with the local address book files on the client machine, and other synchronization issues are caused by lack of access to the address book folder (e.g. network access), permissions, or address book configuration on the Lync server.

This post provides solutions to 4 common issues, and some basics on the Lync address book implementation to further your understanding.

Common Problems & Solutions

Four common problems and their solutions are listed below.

1] The Persistent Message “The address book is preparing to synchronize” in the Lync Client

When the Lync client is run for the first time it chooses a random time between 1 – 59 min to download the Lync address book (from the FE server). The random time is to prevent network storms if a lot of Lync clients are being deployed at the same time.

If you have had the Lync client running continuously at any time for more than 2 hours and this synchronization message is still displayed, there is likely an issue.

The solution here is to delete your existing local Lync address book files and force the download of new ones from the server:

  1. Shutdown the Lync client
  2. Force the Lync client to download the address book immediately the next time it starts:
    • Open the registry to HKLM\Software\Policies\Microsoft\Communicator
    • Modify (or Create) the DWORD  the registry key “GalDownloadInitialDelay” and set it to 0  (that is a zero)
    • This can also be done from the command line:
      • reg add HKLM\Software\Policies\Microsoft\Communicator /v GalDownloadInitialDelay /t REG_DWORD /d 0 /f
  3. Delete the Existing Local Address Book Files:
    • On Windows 7 or Vista machines, open Windows Explorer to the directory:
      • %userprofile%\AppData\Local\Microsoft\Communicator\sip_user@example_domain
    • Delete the files GalContacts.db and GalContacts.db.idx
  4. Restart the Lync client.
    •    The address book should be available in less than an hour.

I have seen this work many times in production deployments.

Jeff Schertz has an excellent blog entry on the process that is used to update the Lync address book and how to force the Lync clients to update – see Updating the Lync 2010 Address Book.

2] The Lync Address Book Website does not have a Valid SSL Certificate Installed

Microsoft knowledge base article 939530 describes this problem well:

The Lync 2010 client or the Office Communicator client does not download the corporate address book and displays a notification: “Cannot Synchronize Address Book”

The resolution section of the KB article details how to verify that the existing certificate is valid, and how to assign another certificate if need be.

3] Symantec Antivirus Running on the Lync Server is Restricting Access to the Address Book File Share

Some versions of Symantec Antivirus running on Windows 2008 server, can cause access issues to network shares.

If you cannot map the Lync address book network share from more than one client and are running Symantec Antivirus, this is a possible cause.

This Microsoft KB article provides the details and the solution: Unable to access Shares “The specified network name is no longer available” when Symantec Endpoint Protection prior to 11.0.4202 (MR4-MP2) or Symantec Antivirus 10.2 are installed on a Windows 2003, 2008 or 2008 R2 Server.

4] VMWare Network Adapter Preventing Access or Causing Sluggish Performance to the Address Book File Share

If you are using VMWare images for either the Lync Front-End or where you are Lync address book file share resides, and are having address book synchronization issues, you should check that your virtual NIC emulator type is set to VXNET3. Problems have been seen when this is set to other emulator types such as E1000.

You can read more about the available VMWare network adapter types here: Choosing a network adapter for your virtual machine.

Address Book Basics

At a high level the server-side Lync address book consists of a Lync address book files and a web service. The majority of Lync clients download and use local copies of the address book files, but the default client policy is to also use the web service if the local address book files are not available. Administrators can control how Lync clients use the Address Book with a Lync client policy setting (see for more details).

The Address Book Files

Lync clients pull down the address book files from the file store configured on their home registrar pool. You can find the address book file store path by looking at the ‘File store’ property of the Lync pool in the Topology Builder (just right-click on the pool name and it is in the left-hand pane). This is the same file store that also contains the:

  1. The File Store for other Lync Web Services (ABFiles, CollabContent, CollabMetadata, DeviceUpdateLogs, DeviceUpdateStore, LMStaticData, MeetingComplianceData, MeetingContent, MeetingFiles, MeetingMetaData and WebAuthStore).
  2. CMS File Store.
  3. Application File Store.

A good first troubleshooting step is to see if the machine where the Lync client is running can access the Lync address book file share.

The Address Book Web Service

The Lync address book also contains a web service, and some clients (such as Lync devices) can use it instead of downloading the address book files.

The URL associated with the address book web query service can easily be found by viewing the configuration information of a signed-in Lync client. Right-click on the Lync client icon in Windows taskbar (or notification tray) and select ‘Configuration Information’. The ‘URL from Server’ gives the internal and external URLs of the address book service.

URL Internal From Server;https://<Lync Pool FQDN>:443/abs/handler
URL External From Server;https://<Lync External Web Service FQDN>:443/abs/handler

You can test the address book via the web service using the Test-CsAddressBookService and Test-CsAddressBookWebQuery cmdlet’s. The Test-CsAddressBookWebQuery cmdlet is more in-depth and tests searching and returning information. The Test-CsAddressBookService cmdlet tests the ability of a specific user to access the address book server, and can be used as follows:

Test-CsAddressBookService –TargetFqdn <pool fqdn> -UserCredential $myCred -UserSipAddress “”

You will need to assign the credentials for example_user to the PowerShell variable $myCred by first doing: $myCred = Get-Credential.


Special thanks to Steve Gover for uncovering the solutions to issues #3 and #4.

Microsoft Next Hop – LyncMD: Troubleshooting the Lync 2010 Address Book

Microsoft TechNet  – Lync Address Book Capacity Planning:

Error message when you log on to Microsoft Office Communicator: “Cannot Synchronize Address Book”

The Lync 2010 client or the Office Communicator client does not download the corporate address book and displays a notification: “Cannot Synchronize Address Book”

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