Outlook 4.4.7 messages

[Migration help]

All are users are setup in Outlook the same way. There is a Exchange client
and POP3 service installed in Outlook 2002. The POP3 is the default service
and email is suppose to be going out via this service using ISP's SMTP
server. All of the workstations are XP or 2000 except the one which does not
work which is Millenium. What happens is sometimes I think emails default to
go out the Exchange server even though they should be going out the default
POP3 service ISP SMTP server. We then get errormessages of 4.4.7 coming from
the Exchange server(server01.hmdlaw.lan) hours after mail has been sent.
They say the email has been delayed. Sometimes the emails work and do go
through the ISP smtp server and other times not. Is the only remedy to
upgrade to XP? DNS and IP settings are the same ofr all workstaions there.
The exchange servr is actually setup with a SMTP connector to another
Exchange server. Frankly I would rather send out via SMTP of ISP like all
the other Outlook clients but it is not working consistently. We upgraded to
SP3 for Outlook 2002 already a few months ago which seemed to fix it for some
time.