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Exchange 5.5 possible email relay

Posted on 2006-07-04
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Last Modified: 2010-03-06
We are running exchange 5.5 and over the last few weeks I have received a number of administrator outbound mail failures (administratot received all failure messages) here is a sample of the failure:

A mail message was not sent due to a protocol error.

      554 delivery error: dd This user doesn't have a yahoo.com.tw account (njaw@yahoo.com.tw) [-5] - mta186.mail.tpe.yahoo.com The message that caused this notification was:


      To:       <njaw@yahoo.com.tw>; <shenchen@mail.xt.hn.cn>; <shenchen@mail.zsptt.zj.cn>; <wengnzw@email.com.cn>; <huchu2008@sina.com>; <alek@sina.com>
      From:     <C277I397z@My Mail Server Ip>
      Subject:  


I quickly realized that my server was sending mail out at a significant rate as I was receiving about 1000 outbound failures a day.  I have tested for open relay at abuse.net and we pass.  Currently we have all incoming mail send to a spam firewall which forwards mail to the exchange server, so I have it setup to only recieve mail from that one IP address.  I ran a virus scan and spyware scan but no luck.  Any other places I can look?
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Question by:Bekster
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by:Bekster
ID: 17036867
I have the routing restrictions set for only "hosts and clients that successfully authenticate" Is it possible that a machine on our lan, who is permitted to send mail, has some type of virus/mail spamming agent running and sending out messages?
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Exchgen earned 500 total points
ID: 17038426
You may still be open for relay..

Please do not rely on exchange 5.5 capability to stop spam.... it just cant do it..

Try and look on the firewall / spamfilter to cut this spam...

if you have added the IP of the firewall anywhere in IMC it would be wise to remove it... just have the default domain added under inbound routes in IMC and nothing else.

Raghu
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