Postfix backward compatibility

Hello folks,

Have another question again.

To setup Postfix, I have followed this tutorial: https://www.linode.com/docs/email/email … -and-mysql">https://www.linode.com/docs/email/email-with-postfix-dovecot-and-mysql.

After the setup when I queried Postfix with this command "systemctl status postfix.service", it reported back that it is running with backward compatibility. My questions is, why it is essential to run Postfix with backward compatibility?

The full output of the "systemctl status postfix.service" command is below:

postfix.service - LSB: Postfix Mail Transport Agent

Loaded: loaded (/etc/init.d/postfix; bad; vendor preset: enabled)

Drop-In: /run/systemd/generator/postfix.service.d

└─50-postfix-$mail-transport-agent.conf

Active: active (running) since Tue 2017-11-14 22:17:32 AEDT; 17s ago

Docs: man:systemd-sysv-generator(8)

Process: 19539 ExecStop=/etc/init.d/postfix stop (code=exited, status=0/SUCCESS)

Process: 19567 ExecStart=/etc/init.d/postfix start (code=exited, status=0/SUCCESS)

CGroup: /system.slice/postfix.service

├─19685 /usr/lib/postfix/sbin/master

├─19686 pickup -l -t unix -u -c

└─19687 qmgr -l -t unix -u

Nov 14 22:17:32 localhost systemd[1]: Starting LSB: Postfix Mail Transport Agent…

Nov 14 22:17:32 localhost postfix[19567]: * Starting Postfix Mail Transport Agent postfix

Nov 14 22:17:32 localhost postfix[19648]: Postfix is running with backwards-compatible default settings

Nov 14 22:17:32 localhost postfix[19648]: See http://www.postfix.org/COMPATIBILITY_README.html for details

Nov 14 22:17:32 localhost postfix[19648]: To disable backwards compatibility use "postconf compatibility_level=2" and "postfix reload"

Nov 14 22:17:32 localhost postfix[19567]: …done.

Nov 14 22:17:32 localhost systemd[1]: Started LSB: Postfix Mail Transport Agent.

Nov 14 22:17:32 localhost postfix/master[19685]: daemon started – version 3.1.0, configuration /etc/postfix

Thanks for help.