Outlook sends local password for mailbox

I have a test network that is NT4 PDC. I have
Exchange 5.5 on a Windows 2000 member server. I
log onto my local machine (not on domain) as
administrator. I try to accesss my Exchange mailbox
using my domain credentials. I get an error that “the
logon credentials supplied were incorrect”. When I
look at the Security logs of the Exchange server I
discover that the Administrator’s credentials are
being passed to the server instead of my domain
credentials. No matter what I do I can’t get my
domain credentials passed to the Exchange server,
only the admin credentials of my local machine,
which the server does not recognize.