Email Sent Being Marked As Spam

One of my clients is trying to send an email to someone who has barracuda spam filter on their systems. the spam filter is rejecting the email and marking the IP address as poor.

The IP address that it is rejecting is not the address of the SMTP server but the PC address (Outlook client). is this normal to check the client pc IP address and not the SMTP server?

The response from the spam filter includes a link to check the IP address which reports the IP address status as "poor".

The problem is this IP address is a dynamic IP assigned by the clients ISP. I tried a couple of IP addresses within the same subnet and they all seem to be marked as poor.

Does anyone have any suggestions on how I can fix this issue?? I have included the (masked) response from the spam filter below:

Code:
From: Mail Delivery System [mailto:Mailer-Daemon@my.webhostsserver.com]
Sent: 21 May 2009 12:51
To: clientemail@clientdomain.com
Subject: Mail delivery failed: returning message to sender

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:

to@emailaddress.com
SMTP error from remote mail server after end of data:
host mail3.emailaddress.com [193.XX.XXX.91]: 554 Service unavailable; Client
host [my.webhostserver.com] blocked using Barracuda Reputation;
[url]

------ This is a copy of the message, including all the headers. ------

Return-path: <clientemail@clientdomain.com>
Received: from [82.XXX.XXX142] (helo=JohnD)
by my.webhostsserver.com with esmtpa (Exim 4.69)
(envelope-from <clientemail@clientdomain.com>)
id 1M76nq-0002SF-Jh; Thu, 21 May 2009 11:51:17 +0000
From: "John Doe" <clientemail@clientdomain.com>
To: "'Paul Smith'" <to@emailaddress.com>
Cc: "'Someone Else'" <someoneelse@adomain.com>
Subject: Week commencing the 30th June
Date: Thu, 21 May 2009 12:51:09 +0100
Message-ID: <003601c9da0a$7365a865$5a30f920$@jdoe@clientdomain.com>
MIME-Version: 1.0
Content-Type: multipart/alternative;
boundary="----=_NextPart_000_0037_01C9DA12.D53A1060"
X-Mailer: Microsoft Office Outlook 12.0
Thread-Index: AcnaCm5j32za/IgbRHavuUl2ZVBwWA==
Content-Language: en-gb