package postfix 3.1.0-3 failed to install/upgrade: il sottoprocesso installato script di post-installation ha restituito lo stato di errore 75

[giulux]

Every time I do apt update:

Configurazione di postfix (3.1.0-3)...

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
newaliases: warning: valid_hostname: numeric hostname: 04
newaliases: fatal: file /etc/postfix/main.cf: parameter mydomain: bad parameter value: 04
dpkg: errore nell'elaborare il pacchetto postfix (--configure):
 il sottoprocesso installato script di post-installation ha restituito lo stato di errore 75
Configurazione di htop (2.0.1-1)...
Elaborazione dei trigger per libc-bin (2.23-0ubuntu3)...
Si sono verificati degli errori nell'elaborazione:
 postfix
E: Sub-process /usr/bin/dpkg returned an error code (1)

ProblemType: Package
DistroRelease: Ubuntu 16.04
Package: postfix 3.1.0-3
ProcVersionSignature: Ubuntu 4.4.0-21.37-generic 4.4.6
Uname: Linux 4.4.0-21-generic x86_64
ApportVersion: 2.20.1-0ubuntu2
AptOrdering:
 htop: Install
 postfix: Configure
 htop: Configure
 NULL: ConfigurePending
Architecture: amd64
Date: Sun May 29 11:00:19 2016
ErrorMessage: il sottoprocesso installato script di post-installation ha restituito lo stato di errore 75
EtcMailname: xub16.04
Hostname: xub16.04
InstallationDate: Installed on 2016-04-30 (29 days ago)
InstallationMedia: Xubuntu 16.04 LTS "Xenial Xerus" - Release amd64 (20160420.1)
PostconfMydomain: 04
PostconfMyhostname: xub16.04
PostconfMyorigin: /etc/mailname
RelatedPackageVersions:
 dpkg 1.18.4ubuntu1.1
 apt 1.2.10ubuntu1
ResolvConf:
 # Dynamic resolv.conf(5) file for glibc resolver(3) generated by resolvconf(8)
 # DO NOT EDIT THIS FILE BY HAND -- YOUR CHANGES WILL BE OVERWRITTEN
 nameserver 127.0.0.1
 search puppunet3
SourcePackage: postfix
Title: package postfix 3.1.0-3 failed to install/upgrade: il sottoprocesso installato script di post-installation ha restituito lo stato di errore 75
UpgradeStatus: No upgrade log present (probably fresh install)

[Rolf Leggewie (r0lf)]

newaliases-related bugs:
bug 1586745
bug 1057100
bug 1531299
bug 820870

[Launchpad Janitor (janitor)]

Status changed to 'Confirmed' because the bug affects multiple users.

[Scott Kitterman (kitterman)]

See the terminal log:

Running newaliases
newaliases: warning: valid_hostname: numeric hostname: 04
newaliases: fatal: file /etc/postfix/main.cf: parameter mydomain: bad parameter value: 04

The hostname is invalid, so the error is correct. This is a local configuration issue and not a packaging bug.