You have an invalid hostname:
Running newaliases
newaliases: warning: valid_hostname: numeric hostname: 04
newaliases: fatal: file /etc/postfix/main.cf: parameter mydomain: bad
parameter value: 04
dpkg: error processing postfix (--configure):
subprocess installed post-installation script
--
package postfix 2.7.0-1 failed to install/upgrade: subprocess installed
post-installation script returned error exit status 75
https://bugs.launchpad.net/bugs/674483
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