Comment 2 for bug 1311385

From log:

Setting up postfix (2.11.0-1) ...
Installing new version of config file /etc/postfix/postfix-files ...
Installing new version of config file /etc/postfix/post-install ...

Postfix configuration was not changed. If you need to make changes, edit
/etc/postfix/main.cf (and others) as needed. To view Postfix configuration
values, see postconf(1).

After modifying main.cf, be sure to run '/etc/init.d/postfix reload'.

Running newaliases
postalias: fatal: open /etc/postfix/aliases/: Not a directory
dpkg: error processing package postfix (--configure):
 subprocess installed post-installation script returned error exit status 1
dpkg: dependency problems prevent configuration of postfix-mysql:
 postfix-mysql depends on postfix (= 2.11.0-1); however:
  Package postfix is not configured yet.

dpkg: error processing package postfix-mysql (--configure):
 dependency problems - leaving unconfigured