package postfix 2.9.1-5 failed to install/upgrade: subprocess installed post-installation script returned error exit status 75

[GillAgain]

I believe the error reports started soon after I enabled Medibuntu packages on 11.10, a month or two into the past. The current error report presented suring the "install" part of an automatic upgrade from 11.10 to 12.04.

ProblemType: Package
DistroRelease: Ubuntu 12.04
Package: postfix 2.9.1-5
ProcVersionSignature: Ubuntu 3.2.0-24.37-generic 3.2.14
Uname: Linux 3.2.0-24-generic x86_64
ApportVersion: 2.0.1-0ubuntu6
Architecture: amd64
Date: Fri Apr 27 07:49:21 2012
ErrorMessage: subprocess installed post-installation script returned error exit status 75
InstallationMedia: Ubuntu 11.10 "Oneiric Ocelot" - Release amd64 (20111011)
SourcePackage: postfix
Title: package postfix 2.9.1-5 failed to install/upgrade: subprocess installed post-installation script returned error exit status 75
UpgradeStatus: Upgraded to precise on 2012-04-27 (0 days ago)

[Clint Byrum (clint-fewbar)]

Hi there GillAgain. Error code 75 means that postfix cannot use your hostname, as it is invalid for email purposes. Check /etc/hostname and /etc/mailname and see if they have any invalid characters such as _'s in them. Some home routers return invalid hostnames and cause this problem.

Closing as Invalid.