یه جایی خوندم اگه Cached Mode را نداشتید ایجاد کنید با این حال این مطلب را هم یه چک کن
Running Exchange 2010 with Outlook 2010 and my Global Address List is not updating when in Cached Mode. When switched to no-cached mode it is up-to-date
I tried the "download address book" under send/receive, but that did not solve the issue
I also deleted all the *.oab files in my Directory
C:\Documents and Settings\User Profile\Local Settings\Application Data\Microsoft\Outlook
...And restarted my Outlook and it seems to work
OR
I've resolved this issue by closing outlook and deleting ost files inside %USERPROFILE%\Local settings\Application data\MIcrosoft\Outlook
After opening Outlook it resynced with Exchange and downloaded updated Address Book