Outgoing Email Is Flagged As Spam

A user in my server trying to send email, but email is flagged as "Absolute Spam" by Spamassassin. It says IP is listed in SBL/XBL.

There is an IP address in "Received-From" part of the headers. That IP is actually listed in several spam databases, but not my server's IP (Below, red and bold).
Email is sent from my server, but how come "From" IP is different from mine?

Headers of the email are below:

Quote:

Received: from [203.215.94.252] (helo=[10.0.0.7])
by server1.kanmonline-server101.net with esmtp (Exim 4.63)
(envelope-from <*********@sweetmail.org>)
id 1HQ3Yj-0007jV-6J
for ************@ezweb.ne.jp; Sun, 11 Mar 2007 00:32:37 +0900
Mime-Version: 1.0 (Apple Message framework v624)
In-Reply-To: <**********************@nm03imap01c.ezweb.ne.jp>
References: <**********************@nm03imap01c.ezweb.ne.jp>
Content-Type: text/plain; charset=ISO-2022-JP; delsp=yes; format=flowed
Message-Id: <98108bd45ea8b8bbd10cc7c35b6fad81@sweetmail.org>
Content-Transfer-Encoding: 7bit
From: =?ISO-2022-JP?B?GyRCOWI2NhsoQiAbJEIwITUqO1IbKEI=?= <**********@sweetmail.org>
Subject: Re:
Date: Sat, 10 Mar 2007 23:32:34 -0800
To: *********@ezweb.ne.jp
X-Mailer: Apple Mail (2.624)