Change root@hostname to different email address - From https://anandarajpandey.com/2014/09/10/how-to-change-default-root-email-address-linux-postfix-centos/
By default, any email sent by system is sent to root@hostname. So critical server errors, log errors, corn jobs alerts e.t.c all are sent to this default email address. To change it to different appropriate email id, we can do this by two ways.
For this example, lets set email to system@mydomain.com
$ vi /etc/aliases
Add email ids at the bottom of the file.
root: system@mydmomain.com
To add multiple email ids, we can simply separate them by comma.
root: system@mydomain.com, linux@mydomain.com
linux@mydomain.com is second email id
$ newaliases
service postfix restart
We can simply create .forward file to the folder root and add email address there.
$ vi /root/.forward
system@mydomain.com
Restart postfix server
$ service postfix restart.