Stripping headers and the main.cf

[jwh99]

I am trying to remove certian headers and my instructions are to add a line in the main.cf to read
header_checks = regexp:/opt/zimbta/postfix/conf/maps/header_checks
Then add lines in in the header_checks file to read
# Sample For Dropping Headers:
#/^Header: IfContains/ IGNORE
/^Received: from 127.0.0.1/ IGNORE
/^User-Agent:/ IGNORE
/^X-Mailer:/ IGNORE
/^X-Originating-IP:/

Problem is when I restart the services on zimbra it replaces the changed main.cf with a default one.

I have 2 questions

1. How do I change the main.cf properly so that it stays through services restarting

2. Am I removing the headers in the right manner.

Thanks for the help.