Comment 16 for bug 1027061

I'm not setting any values in debconf, I'm only installing the package (non-interactive) and doing configuration in puppet also.

You are right that puppet will re-enforce our configuration, however, we are not using the puppet agent, so resetting the value might take up to a few weeks, depending on the amount of changes we perform on our servers around that time.
In this particular case it left postfix open to the internet for about a week, possibly turning our servers into spam proxies. I didn't notice this change until the next run.