As is usually the case with questions posed here, I have tried everything I can think of to get around this problem. I moved one of my workstations into my new AD domain and found that no matter who logs into the machine, even a Domain Admin, they can not access the Exchange 5.5 server. I've tried deleting all of the profiles from the machine, I've tried pulling the machine out of the AD domain and adding it back in. I've checked to make sure that the Outlook security is set to no password. No matter what I've tried, I get the "You do not have permission to access...." when trying to setup a Exchange 5.5/Outlook profle on the computer. I can browse the server where Exchange resides. It also serves as a File Server and I can access all the shares on it. I did not migrate the NT Domain into an AD domain, I created a parallel domain and setup a two way trust between the NT PDC and Active Directory 2003 server. The trust seems to work in any way I can test it and I've moved other machines in this way without problem. Since it happens to anyone who logs into that machine, I can only assume the problem is with the PC itself, and not with the user accounts. But what could that problem be?