Have you set up your account in Outlook 2003?
You should be able to import your account settings from Outlook Express into Outlook 2003.
1. In Outlook, on the File menu, click Import and Export.
2. In the Choose an action to perform box, click Import Internet Mail Account Settings, and then click Next.
3. In the Select the e-mail client to import box, click Microsoft Outlook Express or Microsoft Outlook Express or Microsoft Windows Mail, and then click Next.
4. Make sure that the name that is displayed is the name that you want to use, and then click Next.
5. Make sure that the e-mail address is correct, and then click Next.
6. Make sure that the incoming and outgoing mail servers are correct, and then click Next.
7. Make sure that the account name and password are correct, and then click Next.
NOTE: If you are using an MSN, The Microsoft Network, Post Office Protocol 3 (POP3) account, you may have to select the Log on using Secure Password Authentication (SPA) check box.
8. Click the method that you use to connect to the Internet, and then click Next.
9. Click Finish to import your mail account settings.