My first thought:
Derived from your postfix main.cf, your server is bound to: localhost which pretty much locks it out from the rest of the world.
That's why, when you telnet from localhost to localhost, you see your mail being forwarded to "mail.pixcel.co.za" for further handling, which is the same machine, but it's approaching it from the outside world ip 188.8.131.52.
Now that's a big no go because of the following line in your main.cf:
inet_interfaces = localhost
Change that to:
inet_interfaces = localhost 184.108.40.206
Restart postfix, and your server should now be ready to be conquered by the wonderfull world of spam :-)