Well I haven’t posted in awhile so I thought I would write about this because I just ran into this issue. I made a new user and mailbox, changed their email address, and that user was not appearing under the global address list but would appear under All Users in the address book. In my case I’m running Exchange 2007 and most of my clients are using Outlook 2010.
Step 1. log into the Exchange Management Shell and run:
update-filedistributionservice -identity Servername
Of course change Servername to the real name of your server.
Then Update-GlobalAddressList hit enter, then type the name of the GAL
Step 2. In Outlook manually download the address book by going to: the Send / Receive tab, then click on Send/receive Groups, and in the drop down, click on Download Address Book, then under Information to download, click Full Details. After that the user should now appear in the global address list.