Thanks for the feedback. How do I manage to remove the sender IP from the authentication results?
The entry '/^Authentication-Results:\s+.*/ IGNORE' in /etc/postfix/header_checks does not take effect.
The entry ’header_checks = pcre:/etc/postfix/header_checks’ in '/etc/postfix/main.cf' is really no overwritten by Plesk, if I set with the command 'postconf -e "header_checks = pcre:/etc/postfix/header_checks"'?