Relaying denied error

[JD]

Im getting this relay error. am I missing something in my relay table?
-----------------------------------
Your message did not reach some or all of the intended recipients.

      Subject:  Gastric Band

      Sent:     4/19/2004 3:24 PM

The following recipient(s) could not be reached:

      John Costello (blah at cwnet.com) on 4/19/2004 3:24 PM

            550 5.7.1 <blah at cwnet.com>... Relaying denied
------------------------------------