How to update the Global Address Book in Outlook

When changes occur within the main (Global Address Book) on the Exchange server; computers running Outlook 2010 may not automatically receive the updates. When this happens you may be missing new entries, see non-existent entries, or notice incorrect entries. Updating your address book synchronizes the cached Address Book with the Global address book, and may fix instances of mail that is bounced back to the sender.

Click on FILE / Account Settings / Download address Book
In the Offline Address Book dialog box, make sure that the Download changes since last Send/Receive check box is checked.
Click OK - watch it update... you are done