I know I have probably overlooked the fix but can you send me the link or directions? 
This is the message I keep getting when trying to install:
Package operation failed  

installArchives() failed: Setting up postfix (2.9.3-2~12.04.3) ...

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: 1
newaliases: fatal: file /etc/postfix/main.cf: parameter mydomain: bad parameter value: 1
dpkg: error processing postfix (--configure):
 subprocess installed post-installation script returned error exit status 75
No apport report written because MaxReports is reached already
Processing triggers for libc-bin ...
ldconfig deferred processing now taking place
Errors were encountered while processing:
 postfix
localepurge: Disk space freed in /usr/share/locale: 0 KiB
localepurge: Disk space freed in /usr/share/man: 0 KiB
localepurge: Disk space freed in /usr/share/gnome/help: 0 KiB
localepurge: Disk space freed in /usr/share/omf: 0 KiB
localepurge: Disk space freed in /usr/share/doc/kde/HTML: 0 KiB

Total disk space freed by localepurge: 0 KiB

localepurge: Disk space freed in /usr/share/locale: 0 KiB
localepurge: Disk space freed in /usr/share/man: 0 KiB
localepurge: Disk space freed in /usr/share/gnome/help: 0 KiB
localepurge: Disk space freed in /usr/share/omf: 0 KiB
localepurge: Disk space freed in /usr/share/doc/kde/HTML: 0 KiB

Total disk space freed by localepurge: 0 KiB

localepurge: Disk space freed in /usr/share/locale: 0 KiB
localepurge: Disk space freed in /usr/share/man: 0 KiB
localepurge: Disk space freed in /usr/share/gnome/help: 0 KiB
localepurge: Disk space freed in /usr/share/omf: 0 KiB
localepurge: Disk space freed in /usr/share/doc/kde/HTML: 0 KiB

Total disk space freed by localepurge: 0 KiB

localepurge: Disk space freed in /usr/share/locale: 0 KiB
localepurge: Disk space freed in /usr/share/man: 0 KiB
localepurge: Disk space freed in /usr/share/gnome/help: 0 KiB
localepurge: Disk space freed in /usr/share/omf: 0 KiB
localepurge: Disk space freed in /usr/share/doc/kde/HTML: 0 KiB

Total disk space freed by localepurge: 0 KiB

Setting up postfix (2.9.3-2~12.04.3) ...

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: 1
newaliases: fatal: file /etc/postfix/main.cf: parameter mydomain: bad parameter value: 1
dpkg: error processing postfix (--configure):
 subprocess installed post-installation script returned error exit status 75
Processing triggers for libc-bin ...
ldconfig deferred processing now taking place

Recommended updates:
High-performance mail transport agent postfix(size 1.3MB)
The installationof removal of a software package failed.
Changes for the versions:
Installed version: 2.9.3-2~12.04.3
Available version: 2.9.6-1~12.04.1

Version 2.9.6-1~12.04.1: 

  * New upstream micro-version release (LP: #1117761)


Version 2.9.3-2~12.04.4: 

  * Add back support for NIS authentication that was inadvertently dropped
    (LP: #1068036)

 Thank you Scott