Unable to send email "Relaying denied"

[nick]

Guys Help

I get this message when sending mail from email client, through FC3.
Can anyone help to reslove this probelm?

our message did not reach some or all of the intended recipients.

      Subject:	RE: test message
      Sent:	13/06/2005 23:46

The following recipient(s) could not be reached:

      'nick' on 13/06/2005 23:46
            550 5.7.1 <xxxxx at xxxx.com>... Relaying denied. IP name
lookup failed [192.168.1.2]