[afnog] mail relay problems

[ata]

Hi. This is the qmail-send program at yahoo.com.
I'm afraid I wasn't able to deliver your message to the following addresses.
This is a permanent error; I've given up. Sorry it didn't work out.

<support at domain.com>:
192.168.1.6 failed after I sent the message.
Remote host said: 550 Administrative prohibition


This the message i get when sending mails from yahoo to my network.
It's giving me a night mare.

Moreover mails sent using outlook also bounces back to sender.

please help !!!