Email Access

I have a Linux 9.X web server and have set up email on it. I can use the server console to receive and send email. However, I am unable to access the email from remote locations. I use Outlook Express and have all the settings correct. Each time I attempt to connect to the web server email Outlook Express responds that it cannot find the Server. Also I can upload and download documents using “SSH”. Any suggestions. Help! Thanks in advance.