Sometimes when you update a users name in AD, it doesn't change in Outlook immediately. Updating your address book should force the change.
Updating your Offline Address Book so that it matches the Global Address Book:
- Once you have your Outlook open, go to the Send / Receive tab. Select the option "Send/Receive Groups" and, from that menu, click on the "Download Address Book" option.
- A pop-up window will appear. Check to see that it matches the picture below and click on the "OK" button.
- As it is completing the update, this screen will appear.
Once it is finished, your Offline Address Book should be updated to match the Global Address Book.