How can we remove ourselves from Spam Folder

[Lily]

This sender is very smart. They used our email address as theirs and so when we classify their email as spam we are actually putting our own email address into the spam folder. What can we do? Any solution?
NB: name of our co. has been replaced with xxx for anonimity sake.



Return-path: <sales@xxx.com.sg>
Envelope-to: sales@xxx.com.sg
Delivery-date: Mon, 02 Nov 2009 02:06:00 -0600
Received: from dsl-245-59-137.telkomadsl.co.za ([41.245.59.137]:1588)
by elise.websitewelcome.com with smtp (Exim 4.69)
(envelope-from <sales@xxx.com.sg>)
id 1N4rvJ-0004Pn-TC
for sales@xxx.com.sg; Mon, 02 Nov 2009 02:05:59 -0600
To: <sales@xxx.com.sg>
Subject: Save with Skype and smile your way through 2009
From: <sales@xxx.com.sg>
MIME-Version: 1.0
Importance: High
Content-Type: text/html