Relay of smtp server

[edwardspl at ita.org.mo]

Dear All,

There is a smtp server ( sendmail-8.13.8-2 ) with FC6 System :

For the problem,
1, how to require user's password and allow his / her domain_name (
abc at test.com and 123 at abc.com ) sending mails via smtp server ?
2, Prevent the IP address of smtp server from listing ( eg :
http://cbl.abuseat.org ) ?

Edward.