You might want to call support but the Issue is usually
nano /etc/crontab
You will see that footer:
SHELL=/bin/bash
PATH=/sbin:/bin:/usr/sbin:/usr/bin
MAILTO=root
HOME=/
Change it to too:
SHELL=/bin/bash
PATH=/sbin:/bin:/usr/sbin:/usr/bin
MAILTO=
HOME=/
The messages should be gone.
The problem is that postfix get's a mail for every cron execution and on some systems this setting is set up that way causing this strange mails being routed when you have a * route under mail.