Thank you for your report. It looks like you have the mail-stack-delivery package installed, which is designed to alter postfix's configuration as declared in the package description: "This package modifies postfix's configuration to integrate with dovecot".
If you do not want to have your postfix configuration automatically managed, then why do you have mail-stack-delivery installed? Marking this bug as Invalid, as I think the behaviour you describe is by design. If this is not correct, please explain and then change the bug status back to New. Thanks! ** Changed in: postfix (Ubuntu) Status: New => Invalid -- You received this bug notification because you are a member of Ubuntu Server Team, which is subscribed to postfix in Ubuntu. https://bugs.launchpad.net/bugs/1323704 Title: main.cf silently modified during postfix 2.9.1-4 upgrade on 12.04LTS To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/postfix/+bug/1323704/+subscriptions -- Ubuntu-server-bugs mailing list Ubuntu-server-bugs@lists.ubuntu.com Modify settings or unsubscribe at: https://lists.ubuntu.com/mailman/listinfo/ubuntu-server-bugs