554 Relay Rejected

Dear All, I am getting the following error while sending the email to some of the external domains

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

Subject: RE: hello

Sent: 1/7/2008 11:31 AM

The following recipient(s) could not be reached:

‘test@test.com’ on 1/7/2008 11:32 AM

554 Relay rejected for policy reasons.

Regards

Waqqas

Subject: 554 Relay Rejected

where is the delivery failure coming from? Who is actually rejecting it? 554 is a hard reject so it will never go through unless something about the e-mail changes.