Mail could not be delivered

[Bill]

I am trying to set a user up with Email using Microsoft
Outlook '97. This is only for internal mail messages, no
outside access. So far I have gotten Outlook set up to
where the person is able to receive Email but is not able
to send them. I am receiving an undeliverable Email error
with the message that "mail could not be delivered due to
a problem with the post office".

His setup is no different than other setups we have done?
Any ideas?

Thanks!