Auto complete on Outlook 2003

Where can I go to edit the list of email addresses that appears in Oulook 2003 when one types in the first letter of the individual in the To: field?
When an employee left the company, I renamed her account with a new name. However, now when someone wants to send the new person an email, the autocomplete name that comes up is Newname@domain. It happens on all workstations, so it must be something in the Exchange server (Exchange 2000) but I can’t find it.
I’ve checked in Active Directory’s User, the Exchange general, E-mail addresses, Exchanged Advanced, etc. features and can’t find where the oldname is listed.
Thanks