Ok I fixed half of the problem. Now I can send mails from my own domain but I can't receive mails from let's say yahoo.com.
I solved the problem by adding 2 lines in /etc/postfix/local-host-names
I have added localhost.localdomain.usarmydt.com and
But still I can't receive email from other providers and the strange thing is that I can't find anything about that in the logs. Any ideas ?