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It would appear that your installation is not configured with a valid hostname - you will need to resolve this before postfix will install correctly. You can do this either by editing /etc/postfix/main.cf to set the myhostname configuration parameter to a valid hostname and then completing the installation: sudo vi /etc/postfix/main.cf sudo apt-get -f install Please update this bug report if this resolves your issue. Thanks ** Changed in: postfix (Ubuntu) Status: New => Incomplete -- You received this bug notification because you are a member of Ubuntu Server Team, which is subscribed to postfix in Ubuntu. https://bugs.launchpad.net/bugs/766177 Title: package postfix 2.6.5-3ubuntu0.1 failed to install/upgrade: subprocess installed post-installation script returned error exit status 75 -- Ubuntu-server-bugs mailing list Ubuntu-server-bugs@lists.ubuntu.com Modify settings or unsubscribe at: https://lists.ubuntu.com/mailman/listinfo/ubuntu-server-bugs