To setup your Outlook 2003 to handle your new POP3 e-mail account, please follow the instruction below :- 
 
01. Select Tool > Email Accounts... to start the Options dialog box.
 
02. Click Add a new email account and Next.
 
03. Click POP3 in Server Type and Next.
 

04. In User Information
 - Fill in Your Name, Email Address.
 
05. In Logon Information
 - Fill in full email address in User Name and fill in account password.
 
06. In Server Information
 - Fill in mail.yourdomain.com for Incoming mail server (POP3) and Outgoing mail server (SMTP).

07. Click More Settings...

08. Click on Outgoing Server.
 - Click on My outgoing server (SMTP) requires authentication check box.

9. Go to 'Advanced' tab and change the Outgoing server (SMTP) port number from 25 to 587.

10. Once all information is entered, click on OK button and Next to complete the setup.