smurfkillin

I just started getting a TON of returned mail from various servers, mainly telling me that a message cannot be sent because the user doesnt exist, blah blah. Sample below:

______________________________________
Hi. This is the qmail-send program at triskel.steredenn.net.
I'm afraid I wasn't able to deliver your message to the following addresses.
This is a permanent error; I've given up. Sorry it didn't work out.

<woodyff6sol.com>:
Sorry, no mailbox here by that name. vpopmail (#5.1.1)

--- Below this line is a copy of the message.

Return-Path: <c.silver_hhmperalta.com>
Received: (qmail 28523 invoked by uid 503); 17 Oct 2005 21:17:36 -0000
Received: from unknown (HELO millepattes.com) (61.144.222.80)
by triskel.steredenn.net with SMTP; 17 Oct 2005 21:17:36 -0000
Message-ID: <2.2.32.2005091721143900b7f733mperalta.com>
From: "Carmelo Silver" <c.silver_hhmperalta.com>
Subject: =?ISO-8859-1?B?Rmxhd2xlc3MgRmluYW5jaW5nIFNvbHV0aW9ucw==?=
Date: Mon, 17 Oct 2005 21:14:39 +0000
MIME-Version: 1.0
X-Sender: <c.silver_hhmperalta.com>
In-Reply-To: <dbe701c5ce39$d6f66639$0772b87duq16xx3>
X-Mailer: Windows Eudora Pro Version 2.2 (32)
Content-Type: text/plain;
charset="us-ascii"
Content-Transfer-Encoding: 8bit

ÂHi,

ÂFlawless Home Loan Offer

Âhttp://b.09mort.com/6/index/owner/

______________________________________

Problem is: there is no user named 'c.silver_hhmperalta.com' - this is one of my servers, but it seems that someone is spoofing the domain name and sending emails and i am getting the returned message on my default/catch all address.

IS THERE ANY way to stop this?
thanks