If the your offline copy of the Global Address List is out of sync, you can download a fresh copy

Step-by-step guide

1. In Outlook, click the Send/Receive tab and then click Send/Receive Groups → Download Address Book...
   
   
   
   
2. Uncheck "Download changes since last Send/Receive" and select the Full Details radio-button.
   
   
   
   
3. Click OK to start the download.

Once the address book has been refreshed, close and restart Outlook.  It should now match the online version of the Global Address List.

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