To enable SMTP Authentication in OUTLOOK EXPRESS please follow the following steps :-
1) Open Outlook Express.
2) Click on "Tools" menu and choose "Account"s.
3) Click on "Account" for which you want to enable SMTP authentication and then click "Properties".
4) Click on "Server" and check the check box in front of "My Server
requires authentication". Click on "Finish".
Your "SMTP Authentication" has been enabled in the Outlook Express.