comcast.net recipient address problems

[Chris Jensen]

one of my clients has been having somewhat intermittent problems 
sending mail to comcast.net addresses.  their domain is not the main 
domain of the server.  i've gone ahead and added SPF lines to their 
zone files, is this going to do the trick or are there some other 
issues with comcast that i can't find info about?  this is the error:

SMTP: Address rejected by host
Host 'gateway-r.comcast.net' says:
550 [PERMFAIL] comcast.net requires valid sender domain
and
Reporting-MTA: dns;mailsrv1.kclub.ie
Received-From-MTA: dns;kclubsurfilterx.kclub.ie
Arrival-Date: Mon, 4 Oct 2004 16:02:30 +0100
Final-Recipient: rfc822;[EMAIL PROTECTED]
Action: failed
Status: 5.5.0
Diagnostic-Code: smtp;551 This is not a relay host - mail must be to or 
from host domain.
X-Display-Name: Name - OffSite Mail

if anyone has any insight as to what's going on i would be very 
appreciative!!! thanks in advance!

chris
---------------------------------
Chris Jensen
Vis Dynamics, Inc.
e: [EMAIL PROTECTED]
p: 616.456.6566x28
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