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Stop Exchange 2003 from sending "unknown user" emails..

Posted on 2004-08-04
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Last Modified: 2008-01-16

Like everyone else on the planet, my server gets spammed to oblivion... however, my SBS2003 insists on sending messages back to the spammers with "unknown user" - and a copy of the SPAM!!

I'd much rather silently drop these messages - how do I do that?

also, I guess, is there a good alternative to Spam assassin for Exchange 2k3?
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Question by:WintermuteCL
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robinluo earned 125 total points
ID: 11719603
ESM > Global Settings > Internet Message Format > (right pane) Default > Right click > Properties > Advanced tab > uncheck "Allow non-delivery report"
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by:marc_nivens
marc_nivens earned 125 total points
ID: 11719655
You're getting hit with what we call NDR spam.  Spammers can use it to tell which addresses are valid and which ones are not.  The only way to do this natively is to turn off non-delivery reports.  If you choose to do this, follow these steps:

1.  Launch Exchange System Manager
2.  Expand Global Settings
3.  Click on Internet Message Formats
4.  Open properies on the * entry to the right
5.  Go to the advanced tab, uncheck allow non-delivery reports.

Note that this will stop all NDR's.  The more long term method of dealing with this is to use spam software.
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Expert Comment

by:TomBoland
ID: 11953990
As far as the spam issue is concerned, I dropped SpamAssasin and now go with an external third-party spam service. I use Postini, but there are others out there. It costs about $3.00 per month per Exchange mailbox - not per SMTP address. Scans for virus, too. Keeps 80% of all emails off my servers completely. Junk mail is veiwable through web interface by user. We have been very happy with the False Positive rate. Pretty darn low.

In my example, what happens is that I had to change my MX record to point to Postini's servers and Postini then forwards the mail to me after it scans it. I also use them for outbound mail, so that my Exchange server is not published anywhere. My outbound mail has Postini's IP address on it.

You can lock down your firewall and Exchange server to accept SMTP traffic only from your third-party vendor.

This really limits your exposure to becoming a relay of any sort. Nobody gets to your Exchange server except through the third party spam filtering company.

I would never go back to SpamAssasin (which I actaully like) or client-based spam filtering again.

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