TO enable SMTP authentication in EUDORA please folow the followinig steps :-
1. Open Eudora email client.
2) Click on "TOOL" menu and then click on "OPTIONS".
3) Under the Category heading on the left, click Sending Mail .
4) Select Allow authentication on the right side of the Options window.
You can also do this for your personalities under Tools>> Personalities.
Note: Eudora uses the login name specified on the Checking Mail configuration option,
which is in the format of username@yourdonain.com.
5) Change Secure Sockets When Sending at the bottom of the window to Never.
6) Click OK.
Your "SMTP Authentication" has been enabled in the EUDORA.
