Try learning about SpamAssassin's notfirsthop DNS blacklist option, and why it might be a sensible idea, you utter cretins.
This message was created automatically by mail delivery software.
A message that you sent could not be delivered to one or more of its
recipients. This is a permanent error. The following address(es) failed:
zzzzzzzz@pts.edu
SMTP error from remote mail server after end of data:
host smtp.pts.edu [72.22.0.101]:
554 Service unavailable; Client host [ppsw-5.csi.cam.ac.uk]
blocked using Barracuda Reputation;
http://bbl.barracudacentral.com/q.cgi?ip=86.165.170.59
------ This is a copy of the message, including all the headers. ------
Return-path:
X-Cam-SpamDetails: Not scanned
X-Cam-AntiVirus: No virus found
X-Cam-ScannerInfo: http://www.cam.ac.uk/cs/email/scanner/
Received: from [86.165.170.59] (port=51166 helo=[192.168.1.2])
by ppsw-5.csi.cam.ac.uk (smtp.hermes.cam.ac.uk [131.111.8.155]:587)
with esmtpsa (PLAIN:zzz99) (TLSv1:AES128-SHA:128)
id 1JHf30-0003CD-Il (Exim 4.67)
(return-path ); Wed, 23 Jan 2008 12:49:42 +0000
Mime-Version: 1.0 (Apple Message framework v752.3)
Content-Type: text/plain; charset=US-ASCII; delsp=yes; format=flowed
...
Tony Finch – blog