Question : sendmail authorization?

How do I set up authorization so users that authorize can send email to other domains (relaying)?
What Do I need in the sendmail.mc file? And how do I create the users file? Can I use the existing /etc/passwd

Answer : sendmail authorization?

The generic instructions for enabling SMTP AUTH in sendmail can be found at http://www.sendmail.org/~ca/email/auth.html Depending on what OS your sendmail server uses the steps relating to installing SASL and rebuilding sendmail may not be relevant. Late versions of RedHat include SASL and an a sendmail built with that support, for example.

It is possible to configure SASL to use the existing passwd/shadow files for user authentication. This does limit the clients to only plain text auth mechanisms (PLAIN & LOGIN).