POP3 connection problem

When I install Outlook Express as client on the same machine with Lotus Domino Server,I can easily download my emails;the connection between my Outlook express and Domino server is fine for that case.I have a Person document,internet password,and mail folder on the server,the POP3 task is running.However,when I install Outlook on a different machine and try to access my Domino server for mail downloading,the connection with the server is not established.