The easiest way to do this is simply connect to Outlook Web Access, and query the GAL directly (OWA uses the GAL no the OAB like Outlook running in cached mode does). The User/Mailbox IS listed on the Server But NOT in Outlook.
Remember, if you are looking at the Global Address List in Outlook then you are NOT looking at the Servers Global Address List*.
Outlook 2003 (and older)* clients get their OAB from a public folder, Outlook 2007 (and newer) clients can get their OAB from 'Web-based distribution' (basically form the website on the Exchange (or Exchange CAS) server.
So there are three factors stopping you seeing that new user on the GAL (, however if that’s not an option, read on).
Quite often all Administrators, even Exchange Administrators simply refer to the users they see in the Address section of Outlook casually as the GAL for ease of reference, but really more often than not, you are looking at the OAB.
However sometimes in large complex organisations we have a situation where a new joiner joins and their colleagues want to email them immediately, but they don’t appear in Outlook for them so they call the Helpdesk “Why isn’t Joe Bloggs in the GAL??
If your company is moving from Exchange to another email system, or if you want a quicker response time when addressing emails, you can also add items from the GAL to your locally-stored contacts folder in Outlook. Highlight all the entries that you’d like to export to your local contacts folder.