In your mail manager/ add remove email accounts, there is a link next to each email account "Outlook (Express) AutoConfig" Download that file and run it onyour PC, all you need to do is add your password when its loaded.
One other note, you might need to change the SMTP setting to the one your ISP gives you, because as it has been stated many times in the forum, Port 25 is being blocked by many ISPs to stop SPAM.
Your pop3 settings should be like this:
User: whatever

mydomain.com
pop3: mail.mydomain.com
smtp: mail.mydomain.com
pass: secret
or if port 25 is blocked
User: whatever

mydomain.com
pop3: mail.mydomain.com
smtp: smtp.myisp.com
pass: secret