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Hi all, 
 
I have a catch all account and 2 email addresses setup. 
 
Info &amp;&nbsp;reception 
@mycompany.com 
 
Yesterday and today I have suddenly received 1000+ return emails from mail delivery system, saying it was unable to deliver to this recipient. It looks like a spammer is sending on behalf of our email address to 1000s of email addresses. 
 
How can I go about preventing this? 
 
exmaple 
----------------------- 
Your message did not reach some or all of the intended recipients. 
 
&nbsp; &nbsp; &nbsp; Subject: &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Can't find you in building 
&nbsp; &nbsp; &nbsp; Sent: &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;21/05/2009 19:25 
 
The following recipient(s) cannot be reached: 
 
&nbsp; &nbsp; &nbsp; |donald.otoole@petrymedia.com on 21/05/2009 19:30 
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; The e-mail account does not exist at the organization this message was sent to. &nbsp;Check the e-mail address, or contact the recipient directly to find out the correct address. 
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &lt;exchange.petrymedia.com 
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Many thanks
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Hi all,

I have a catch all account and 2 email addresses setup.

Info & reception
@mycompany.com

Yesterday and today I have suddenly received 1000+ return emails from mail delivery system, saying it was unable to deliver to this recipient. It looks like a spammer is sending on behalf of our email address to 1000s of email addresses.

How can I go about preventing this?

exmaple
-----------------------
Your message did not reach some or all of the intended recipients.

 Subject:	Can't find you in building
 Sent:	21/05/2009 19:25

The following recipient(s) cannot be reached:

 |donald.otoole@petrymedia.com on 21/05/2009 19:30
 The e-mail account does not exist at the organization this message was sent to. Check the e-mail address, or contact the recipient directly to find out the correct address.
 <exchange.petrymedia.com 
----------------------

Many thanks

Real spam problem - someone sending on behalf of our email addresss

Various techniques are used to prevent email spam (unsolicited bulk email). No technique is a complete solution to the spam problem, and each has trade-offs between incorrectly rejecting legitimate email (false positives) vs. not rejecting all spam (false negatives) - and the associated costs in time and effort. Anti-spam techniques can be broken into four broad categories: those that require actions by individuals, those that can be automated by email administrators, those that can be automated by email senders and those employed by researchers and law enforcement officials.

AntiSpam

Within Internet message handling services (MHS), a message transfer agent or mail transfer agent (MTA) or mail relay is software that transfers electronic mail messages from one computer to another using a client–server application architecture. A MTA implements both the client (sending) and server (receiving) portions of the Simple Mail Transfer Protocol (SMTP). The terms mail server, mail exchanger, and MX host may also refer to a computer performing the MTA function. The Domain Name System (DNS) associates a mail server to a domain with mail exchanger (MX) resource records containing the domain name of a host providing MTA services.