o.k what you need to do is as follows :-
assuming ou are using /etc/hosts file as the lookup entry and not DNS , and you can see the mail server on your network :-
see if you can telnet to mail server on port 25
i.e. telnet mail_server 25
( if this fails then theres no point continuing , check if mailserver is listening on port 25 , and have access to it)
1. add the entry for mail server in /etc/hosts file
2. edit /etc/sendmail.cf
where it has DS
add in something like DSsmtp:smtp_mail
where smtp_mail is the netry in hosts file for mail
server
3. in /etc create a file netsvc.conf ( if not already there)
and add , hosts = local
4. restart sendmail
5. try sending test mail
HTH