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 returned error exit status 75
Setting up procmail (3.22-18ubuntu1) ...
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 returned error exit status 75
Setting up procmail (3.22-18ubuntu1) ...