Comment 2 for bug 814436

Thank you for taking the time to report this bug and helping to make Ubuntu better.

Looking at your dpkg installation log I see this postfix error:

Running newaliases
postconf: warning: valid_hostname: invalid character 40(decimal): (none)
postconf: fatal: unable to use my own hostname

This means that one of postfix's config files contains an error, which is causing it to stop the package installation process. As this constitutes a problem with your local configuration and not an error in postfix, I need to close this bug as invalid.

However, in order for you to solve your problem, I can suggest two things:

1) Please carefully review your postfix configuration, the files in /etc/postfix/ and possibly /etc/aliases, for any errors.
2) Review the postfix documentation if you have any doubts: https://help.ubuntu.com/community/Postfix
3) If you're still unable to configure postfix so it works correctly, you can ask for help by posting a question here: https://answers.launchpad.net/ubuntu/+source/postfix

Thanks for your report!