1) Undo the changes you made in /etc/hosts. There must be a line:
127.0.0.1 localhost.localdomain localhost
To solve the isuue, run these commands:
echo server1.example.com > /etc/hostname
/bin/hostname -F /etc/hostname
replace server1.example.com with your full hostname in the above commands.
Then edit the file /etc/hosts and append the your full domainname to the line:
10.1.250.5 firestorm.localdomain firestorm
Then edit postfix main.cf and replace localhost.localdomain with your full hostname. Then restart postfix.