/var/log/mail.log is full of these I wonder where I should.
│Jul 5 19:06:01 box postfix/master[2302]: reload -- version 3.6.4, configuration /etc/postfix
│Jul 5 19:06:02 box postfix/postfix-script[8399]: refreshing the Postfix mail system
│Jul 5 19:06:02 box postfix/master[2302]: reload -- version 3.6.4, configuration /etc/postfix
│Jul 5 19:06:02 box postfix/postfix-script[8447]: refreshing the Postfix mail system
│Jul 5 19:06:02 box postfix/master[2302]: reload -- version 3.6.4, configuration /etc/postfix
│Jul 5 19:06:03 box postfix/postfix-script[8477]: refreshing the Postfix mail system
│Jul 5 19:06:03 box postfix/master[2302]: reload -- version 3.6.4, configuration /etc/postfix
A reboot did not fix the problem. but later on
a systemctl stop postfix
and ~10 secs and started it again and problem as not repeated.
I wonder where I should look next time. /var/log/mail.* did not have anything specific when the logging started.