First you need to create the email account in order to configure it in Outlook 2003.

Once created, open the Microsoft Outlook 2003 program and follow these steps to configure it:

Within the program, go to Tools -> Email Accounts.

In the window that appears, select Add a new email account, and proceed to the next step with Next.

The Server Type that you have to choose is POP 3.

In the POP3 email configuration, you have to fill in the fields as follows:
User information:
Your name: The name you want to appear when sending an email.
Email address: The email you are configuring [email protected]
Server information: Incoming Mail Server (POP3): mail.su-dominio.com
Outgoing Mail Server (SMTP): mail.su-dominio.com
Login information:
User Name: You must enter the full name of your email account, in this example, [email protected].
Password: The password for the email account.

Once filled in, select: More settings...

In the new window that appears after selecting More settings, select the Outgoing Server tab, and check My outgoing server (SMTP) requires authentication.

Once you have checked it, click OK to return to the previous screen, and select OK again. By clicking Finish, the email account will be configured in Outlook 2003.