Your hosts file is incorrect, the following line:
should be like this:
127.0.0.1 localhost.platinium.no localhost
I also asked you to run the following command:
127.0.0.1 localhost.localdomain localhost
You should run that command as-is without changing anything or entering your hostname etc. and using backticks surrounding the word `hostname`.
According to those dig results you appear to have no A or MX records on that DNS server, so I'm confused as to how this server has been previously delivering mail to the accounts.