[CentOS] Question on mail

All of a sudden I am getting this error this morning.
--------------------------------------
 
<<< 553 5.3.0 Spam blocked see: 
http://ordb.org/lookup/?host=mp;{client_addr}
501 5.6.0 Data format error

Content-Type: message/delivery-status
Action: failed
Status: 5.3.0
Diagnostic-Code: SMTP; 553 5.3.0 Spam blocked see: 
http://ordb.org/lookup/?host=mp;{client_addr}
Last-Attempt-Date: Thu, 27 Mar 2008 09:06:03 -0400

-------------------------------------------
Mail has been working fine for me for a very long time.
I goto the address http://ordb.org and I get no page.
Is this because this site is down or am I considered spam all of a sudden?

Thanks,

Jerry