When you get an error message as the one stated below, you may need to check if SMTP Authentication is enabled in your Outlook Express.
"The message could not be sent because one of the recipients was rejected by the server. The rejected e-mail address was 'firstname.lastname@example.org'. Subject 'Read: Test Subject', Account: 'mail.yourdomain.com', Server: 'mail.yourdomain.com', Protocol: SMTP, Server Response: '503 This mail server requires authentication when attempting to send to a non-local e-mail address. Please check your mail client settings or contact your administrator to verify that the domain or address is defined for this server.', Port: 25, Secure(SSL): No, Server Error: 503, Error Number: 0x800CCC79"?
You may refer to flash tutorial below on how to enable SMTP Authentication on your e-mail account,
For instructions on how to configure your e-mail account with other e-mail programs, please visit,