package operation fails but gives no reason why

[pleabargain]

Distributor ID: Ubuntu
Description: Ubuntu 21.04
Release: 21.04
Codename: hirsute

I update my machine
updater runs
then invariably I get a message that
"package operation fails"
but no details
ergo
this bug report

ProblemType: Bug
DistroRelease: Ubuntu 21.04
Package: update-manager 1:21.04.10
ProcVersionSignature: Ubuntu 5.11.0-25.27-generic 5.11.22
Uname: Linux 5.11.0-25-generic x86_64
ApportVersion: 2.20.11-0ubuntu65.1
Architecture: amd64
CasperMD5CheckResult: unknown
Date: Thu Jul 29 09:48:58 2021
GsettingsChanges:

InstallationDate: Installed on 2015-08-23 (2166 days ago)
InstallationMedia: Ubuntu 14.04.3 LTS "Trusty Tahr" - Beta amd64 (20150805)
PackageArchitecture: all
SourcePackage: update-manager
UpgradeStatus: Upgraded to hirsute on 2021-07-26 (2 days ago)
modified.conffile..etc.default.apport:
 # set this to 0 to disable apport, or to 1 to enable it
 # you can temporarily override this with
 # sudo service apport start force_start=1
 enabled=0
mtime.conffile..etc.default.apport: 2021-01-13T09:36:03.851337

[Julian Andres Klode (juliank)]

You can read /var/log/apt/term.log yourself. Embedding that nicely seems hard, but then again, apport should have shown you the messages when you reported the bug?

As the log tells you, you have installed the postfix mail server, but configured an invalid hostname "04":

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