1. Open Outlook Express.
2. Click the "Tools" menu and select "Accounts..."
3. From "Internet Accounts" select "Add" and "Mail".
4. When the "Internet Connection Wizard" opens, type the name you want displayed on your email messages in the text box (i.e. John Smith) and click next.
5. On the "Internet Email Address" screen, enter your email address in the text box (i.e. jsmith@yourdomain.com) and click next.
6. On the "E-mail Server Names" screen, select POP3 as your server type in the pull-down, enter your incoming mail (POP3) server (i.e. mail.yourdomain.com) and outgoing mail (SMTP) server (i.e. mail.yourdomain.com) in the appropriate text boxes and click next.
7. Type your account name and password used for login in the text boxes provided on the "Internet Mail Logon" screen and click next.
8. Be sure to check/enable "My outgoing server (SMTP) requires authentication."
9. Click "Finish."

If you've configured everything correctly, you should be able to "send and receive" with no errors.