Question : Sendmail - simple step by step for smtp server set up to authenticate - users send from  anywhere to anywhere

Here's the scenario - very very simple

On Redhat Enterprise ver 3 ...

Need smtp server of sendmail to accept "outbound" email sent by only users who authenticate ... users may be on LAN with the mail server and users may be connecting to smtp server from anywhere in internet.  We want them to have their email clients do a plain text login into the smtp server before it'll relay their outbound email.

I've enabled the generic authentication in the sendmail.mc file.

define(`confAUTH_OPTIONS', `A p')dnl
   ....
define(`confAUTH_OPTIONS', `A')dnl
TRUST_AUTH_MECH(`DIGEST-MD5 CRAM-MD5 LOGIN PLAIN')dnl
define(`confAUTH_MECHANISMS', `DIGEST-MD5 CRAM-MD5 LOGIN PLAIN')dnl
 ....
Questions include:

1.  what do I need to add to the "access db" to allow outbound relay from any IP (on lan or wan)
2.  can I have users use the same username/password we set up for them to use when connecting to get POP(3) email?  ... Do I really need to set up a separate username/pwd file/db?
3.  What else do I need to do?

Thanks for any / all help!  

Answer : Sendmail - simple step by step for smtp server set up to authenticate - users send from  anywhere to anywhere

I suspect that the misconfigured DNS is part of your problem. What you should have in the DNS is  A and PTR records for my-server.mydomain.com and CNAME records for smtp.myrealdomain.com point to the my-server.mydomain.com. That sort of mis-configuration may cause saslauthd to lookup the wrong user@realm when it attempts to authenticate the user.