sendmail auth (smtp auth) implementation

[sekhar_vrc]

Dear sir

                 I want to use "smtp auth" feature in the sendmail.i have configured my local lan
and created some users on my redhat linux server 9.0 with sendmail .
I am able to send the mails to outside my network  xyz@yahoo.com   etc.

But i want to use the SMTP AUTH implement feature which will restrict users of my lan
from send mails until /unless they possess username/password on my mail
(sendmail ) server.
The ip based restriction can be done using /etc/mail/access file but
i want to restict the user based restiction i.e the mail sender should possess
valid username/password in my Local mailserver.
In other words my sendmail server should send mails only if i  enable  "My outgoing server requires authentication" and submit the right username/password.
in client side

Please guide me
sekhar