Can’t download POP3 mail from Sendmail

We have a Windows NT domain and use Linux Senmail for email. The users download their email to Outlook clients. I have set up a new Linux sendmail server (Suse 7.3) to replace the old one. I can send messages from Outlook but not receive them. I have checked the inted.conf file and the POP3 service is running, I did activate SMTP but that made no difference so I have stopped it. I can FTP and telnet to the Linux box successfully. Any suggestions gratefully recieved.