1) Open /etc/mail/sendmail.mc
Add following line in last
define(`SMART_HOST’,`Some_SMTP_Server’)
2) Execute following to update /etc/mail/sendmail.cf file
make -C /etc/mail/
Now in sendmail.cf you can see Smart host entry
root@prg-vm:~# grep Some_SMTP_Server /etc/mail/sendmail.cf
DSSome_SMTP_Server
3) restart or reload sendmail
root@prg-vm:~# /etc/init.d/sendmail restart
[ ok ] Restarting Mail Transport Agent (MTA): sendmail.
root@prg-vm:~#
4) Verify logs
May 14 06:47:37 prg-vm sm-mta[9268]: s4E5l2QC009268: from=x@xxx.xx, size=10, class=0, nrcpts=1, msgid=<201405140547.s4E5l2QC009268@prg-vm.xxxxx>, proto=SMTP, daemon=MTA-v4, relay=localhost [127.0.0.1]
May 14 06:47:37 prg-vm sm-mta[9270]: s4E5l2QC009268: to=xxxx@xxxx.xxx, delay=00:00:12, xdelay=00:00:00, mailer=relay, pri=120010, relay=SOme_SMTP_Server. [xx.xx.xx.xx], dsn=2.0.0, stat=Sent (Ok: queued as 219F0387DF)