Port 143 not connected

Hi everyone, I have a client who has XP. I'm having a difficult time in setting up their Outlook Express 6. It gave me the error message 800cccd1 saying the username and password was not right. When I worked telnet to send to their website address through 143 port it told me it was not connected. I have to use this port according to the ISP. I disabled the Windows Firewall and Norton Antivirus but still having problems. I ran it in safemode with networking but still had the error. Any ideas?? Thanks Craig