Open Outlook Express and click on the Tools menu. Select Accounts.
Click Add account and select Mail.
Enter your name as you would like it to appear in the From: field for the outgoing messages.
Enter the email address which the others will use to send email messages to you.
Incoming mail server (POP3/IMAP server): yourdomainname.com
Outgoing mail server (SMTP server): yourdomainname.com
Username: please use the full e-mail account name. Example: instead of you.
Now click once on the newly created account, and choose Properties. Go to the Servers tab and select the My server requires authentication checkbox.
If you use POP3 and want the messages to be kept on the server, choose the Advanced tab and check Leave a copy of messages on server, click OK.
You are done!
Please make sure that you check your incoming e-mail messages before trying to send any. Most servers use the POP-before-SMTP scheme, which disallows sending messages without checking your mail.