To disable backwards compatibility use “postconf compatibility_level=2” and “postfix reload”など、メッセージが出た場合。

私のラズパイのLogwatchでは、下記のようにpostfixでエラーが出ました。
[crayon]
1 Feb 15 14:19:19 raspberrypi postfix[556]: Postfix is running with backwards-compatible default settings
1 Feb 15 17:15:59 raspberrypi postfix[545]: Postfix is running with backwards-compatible default settings
1 Feb 15 17:15:59 raspberrypi postfix[545]: To disable backwards compatibility use “postconf compatibility_level=2” and “postfix reload”
1 Feb 15 14:28:14 raspberrypi postfix[604]: To disable backwards compatibility use “postconf compatibility_level=2” and “postfix reload”
1 Feb 15 14:56:16 raspberrypi postfix[626]: Postfix is running with backwards-compatible default settings
1 Feb 15 14:28:14 raspberrypi postfix[604]: See http://www.postfix.org/COMPATIBILITY_README.html for details
1 Feb 15 14:40:24 raspberrypi postfix[621]: See http://www.postfix.org/COMPATIBILITY_README.html for details
1 Feb 15 17:15:59 raspberrypi postfix[545]: See http://www.postfix.org/COMPATIBILITY_README.html for details
1 Feb 15 12:19:21 raspberrypi postfix[543]: See http://www.postfix.org/COMPATIBILITY_README.html for details
1 Feb 15 14:24:23 raspberrypi postfix[611]: See http://www.postfix.org/COMPATIBILITY_README.html for details
1 Feb 15 14:56:16 raspberrypi postfix[626]: See http://www.postfix.org/COMPATIBILITY_README.html for details
1 Feb 15 14:34:39 raspberrypi postfix[588]: Postfix is running with backwards-compatible default settings
1 Feb 15 14:28:14 raspberrypi postfix[604]: Postfix is running with backwards-compatible default settings
1 Feb 15 14:34:39 raspberrypi postfix[588]: See http://www.postfix.org/COMPATIBILITY_README.html for details
1 Feb 15 14:24:23 raspberrypi postfix[611]: Postfix is running with backwards-compatible default settings
1 Feb 15 12:19:21 raspberrypi postfix[543]: Postfix is running with backwards-compatible default settings
1 Feb 15 14:40:24 raspberrypi postfix[621]: To disable backwards compatibility use “postconf compatibility_level=2” and “postfix reload”
1 Feb 15 14:56:16 raspberrypi postfix[626]: To disable backwards compatibility use “postconf compatibility_level=2” and “postfix reload”
1 Feb 15 12:19:21 raspberrypi postfix[543]: To disable backwards compatibility use “postconf compatibility_level=2” and “postfix reload”
1 Feb 15 14:34:39 raspberrypi postfix[588]: To disable backwards compatibility use “postconf compatibility_level=2” and “postfix reload”
1 Feb 15 14:24:23 raspberrypi postfix[611]: To disable backwards compatibility use “postconf compatibility_level=2” and “postfix reload”
1 Feb 15 14:19:19 raspberrypi postfix[556]: See http://www.postfix.org/COMPATIBILITY_README.html for details
1 Feb 15 14:19:19 raspberrypi postfix[556]: To disable backwards compatibility use “postconf compatibility_level=2” and “postfix reload”
1 Feb 15 14:40:24 raspberrypi postfix[621]: Postfix is running with backwards-compatible default settings
[/crayon]

このような時には、下記をmain.cfに追加して、postfixを再起動させました。
そうしたら、エラーがなくなりました。
[crayon]
$ sudo vi /etc/postfix/main.cf
————————————————————–
#下記を追加する。
append_dot_mydomain=no
mynetworks_style=subnet
smtputf8_enable=no
compatibility_level=2
————————————————————–
$ sudo /etc/init.d/postfix restart
$ sudo /etc/init.d/dovecot restart
[/crayon]