If your ISP does not provide SMTP server service for your use, you may use the Doteasy mail server for SMTP. You will need to specify your Outlook Express to authenticate in order for the SMTP server to accept your outgoing email.
Your SMTP setting will be mail.yourdomain.com
You will find the server authentication checkbox under Outgoing Mail Server in the "Servers" tab.
For more details, please visit: http://www.doteasy.com/tutorials/outlook-express/smtp.cfm