Returned mail: Recipient address rejected: User unknown in relay recipient table (from [10.1.0.189])

[Mail Delivery Subsystem <MAILER-DAEMON@xxxxxxxxxxxxxxxxxxxxxx>]

The original message was received at Sat, 12 Jan 2008 02:07:40 +0900 (JST)
from 222100.unitednetworx.com [87.121.18.100] (may be forged)

   ----- The following addresses had permanent delivery errors -----
<linuxx@xxxxxxxxxxxx>

Reporting-MTA: dns; mg01vsv.sv.jcnet.ad.jp
Arrival-Date: Sat, 12 Jan 2008 02:07:40 +0900 (JST)

Final-Recipient: RFC822; linuxx@c3-net.ne.jp
Action: failed
Status: 5.1.1
Remote-MTA: DNS; [10.1.0.189]
Diagnostic-Code: SMTP; 550 5.1.1 <linuxx@c3-net.ne.jp>: Recipient address 
rejected: User unknown in relay recipient table
Last-Attempt-Date: Sat, 12 Jan 2008 02:07:51 +0900 (JST)

--- Begin Message ---

To:	<linuxx@xxxxxxxxxxxx>
Subject:	SALE 74% OFF on Pfizer
From:	"admin@xxxxxxxxxx" <linuxx@xxxxxxxxxxxx>
Date:	Sat, 12 Jan 2008 02:07:38 +0900 (JST)

--- End Message ---