After you install postfix, then you may wnat to have root’s email sent to a real email address. This will help to send cron jobs to you.
Edit the /etc/aliases file and add your username and external email address.
# root: firstname.lastname@example.org
Now run this command:-
Now restart Postfix:-
# service postfix restart
and to test, run the following command:-
# echo test | mail -s "test message" root