Suspicious failure mail

[ashfame]

My sister uses her email to send mails from hotmail account to recipients (not flodding the To list rather individually) but now she gets a mail like this which looks suspcious to me. Please have a look at the content :

This is the Postfix program at host zimbra4.ocpwebserver.com.

I'm sorry to have to inform you that your message could not
be delivered to one or more recipients. It's attached below.

For further assistance, please send mail to <postmaster>

If you do so, please include this problem report. You can
delete your own text from the attached returned message.

The Postfix program

<abhay@appenterprises.com>: host ns.indiaaccess.com[202.71.139.77] said: 550
5.7.1 Email rejected due to sending server misconfiguration - see
*www.ordb.org/faq/#why_rejected (in reply to MAIL FROM command)



--Forwarded Message Attachment--
From: <my sis email address>
To: <list of email address she uses to send the mail>
Subject: hi
Date: Sun, 6 Jul 2008 20:50:40 +0530

# Dear friend:

#

We are an electronic products wholesale .Our products are of high quality and low price. If you want to do business , we can offer you the most reasonable discount to make you get more profits. We are expecting for your business.

#


Please visit our website: *www.digitaltradecn.com/

#


E-mail : digitaltradecn@188.com

#


Looking forward to your contact and long cooperation with us!

Our mainly products such the phones, PSP, display TV, notebook, video, computers, Mp4, GPS, xbox 360, digital cameras and so on.

Welcome to visit our website!

Any one knows about it? How is this spammer got the mail addresses of those people who were send mail by my sister?

P.S. - She is on hotmail