I am getting an error message to unknow user on my domain. I would like to know is this just a phishing spam email or it was really send from our domain? I have changed our domain name to OURDOMAIN.COM

I have Exchange 2010 installed.

Body of the email is

Delivery has failed to these recipients or distribution lists:

sales
The recipient's e-mail address was not found in the recipient's e-mail system. Microsoft Exchange will not try to redeliver this message for you. Please check the e-mail address and try resending this message, or provide the following diagnostic text to your system administrator.
Sent by Microsoft Exchange Server 2007 



Diagnostic information for administrators:

Generating server: murraygroup.local

[email protected]
#550 5.1.1 RESOLVER.ADR.RecipNotFound; not found ##

Original message headers:

Received: from ironport.mih.co.uk (10.10.29.9) by
 mih-exca-01.murraygroup.local (10.10.29.133) with Microsoft SMTP Server id
 8.3.106.1; Fri, 29 Jun 2012 12:36:12 +0100
Received: from glamf04.netintelligence.com (HELO mailfilter.iomart.com)
 ([62.128.193.114])  by ironport.mih.co.uk with SMTP; 29 Jun 2012 12:42:48
 +0100
Received: from glamta4.netintelligence.com(localhost.localdomain[127.0.0.1])
 by mailfilter.iomart.com ; Fri, 29 Jun 2012 12:37:18 BST
Received: from [195.43.137.66] ([195.43.137.66])    by
 glamta4.netintelligence.com (8.13.1/8.12.8) with ESMTP id q5TBbH4j022142   for
 <[email protected]>; Fri, 29 Jun 2012 12:37:18 +0100
Date: Fri, 29 Jun 2012 12:37:17 +0100
Message-ID: <20120629145229.4C2A817231D8A7958044@SONW>
From: Ines Hampton <[email protected]>
To: sales <[email protected]>
Reply-To: Marguerite Soto <[email protected]>
Subject: User sales
MIME-Version: 1.0
Content-Type: text/plain; charset="utf-8"
Content-Transfer-Encoding: 7bit
Return-Path: [email protected]



eporting-MTA: dns;murraygroup.local
Received-From-MTA: dns;ironport.mih.co.uk
Arrival-Date: Fri, 29 Jun 2012 11:36:12 +0000

Final-Recipient: rfc822;[email protected]
Action: failed
Status: 5.1.1
Diagnostic-Code: smtp;550 5.1.1 RESOLVER.ADR.RecipNotFound; not found
X-Display-Name: sales