Comment 2 for bug 2000446

Thanks for taking the time to report this bug and trying to make Ubuntu better.

This is the installation error:

Preparing to unpack .../04-postfix_3.6.4-1ubuntu1_amd64.deb ...
/etc/postfix/main.cf.proto modified, not updating.
/etc/postfix/master.cf.proto modified, not updating.
grep: /etc/postfix/master.cf: No such file or directory
grep: /etc/postfix/master.cf: No such file or directory
/var/lib/dpkg/tmp.ci/preinst: 175: retry_warning: not found
dpkg: error processing archive /tmp/apt-dpkg-install-fsuCF5/04-postfix_3.6.4-1ubuntu1_amd64.deb (--unpack):
 new postfix package pre-installation script subprocess returned error exit status 127

Could you confirm if you have the file /etc/postfix/master.cf in place? There is nothing much than that we can infer from the logs.

I am setting this bug to Incomplete while we wait for more information, once you add it please set it back to New and we will revisit it.