Outlook 2003 keeps getting addresses from previous Exchange 5.5 server it was pointed to after changing it to new server Exchange 2003

The previous exchange 5.5 server was giving an org name of '..' this being unupgradeable, I installed a new Exchange 2003 server and am using mailbox forwarding to slowly move mailboxes by exporting the mailbox to a pst from the old exchange 5.5 and then importing it into the new exchange 2003 server.  I have giving them oldserver.com and newserver.com and forward the mailboxes internally between the two servers so that everyone can communicate.  It's nasty it's ugly but its working.  The snag I've run into is now Outlook 2003 clients seem to somehow keep populating new email messages with the old servers email references, the new server then getting these messages freaks out and says it can't deliever them as they aren't addressed based on it's address book x400 x500 whatever exchange addresses are wrong, thus the new exchange 2003 server just doesn't know what to do and returns them failed.

In the outlook client when I look at the address books I can see the address list from the old server.. At one point someone had tried to upgrade this and did have the active directory connector running and AD was polluted with the exchange 5.5's address list.. however all mailboxs users now have Exchange 2003 mailboxes and so the AD should have only references to their proper exchange 2003 x400 references?  Is the global address list coming from AD?  Is Outlook managing to contact the old exchange 5.5 when connected to the exchange 2003 server?  When I take outlook 2003 offline and try to view the old address list, it can't display it so I don't think Its on the machine, but it's coming from somewhere and causing messages to fail to be sent..

HELP!