This is Fedora you are using.
On fedora
yum or
rpm command is used.
Use:
Code:
yum install <package_name>
Code:
yum install postfix
And you're using old Fedora which doesn't have support now.
You should use latest Fedora, i.e.,
Fedora 19 Code name: Schrodinger's Cat released on 2nd July 2013.
You can also use Fedora 17 or 18, still the support is available for them.