Global Address List Not Updating

Hello there! And I hope you can help me in my dilemma. We have a 2007 Exchange Server, and we are using 2007 Outlook clients. The issue is that in cached mode, the clients are not updating after the users have been deleted. We have users still in there from being delete months ago. I’ve tried to do some research on the issue to no avail. Any help is greatly appreciated! Thanks Kris