exchange 2003 Inbound Recipient Filtering at smtp level doesn't work

Posted on 2004-08-11
Medium Priority
Last Modified: 2011-09-20
I wan't to use the filter recipients rules at smtp level as defined in Exchange 2003.

My intranet domain is SOLID-DYNAMICS.OFFICE

I receive emails for domain SOLID-DYNAMICS.COM and SOLID-DYNAMICS.FR

I've configured my server properly (it's seems) (I've just upgrade my serveur in EXC2003, we have a EXC2000 Server before)

I've read and applyed the document downloaded at : http://download.microsoft.com/download/9/4/d/94df821b-45fe-48fa-a866-dec23513d700/WN2k3.exe named "What's new in excahnge 2003" chapter : "Inbound Recipient Filtering page 166".

When I telnet my server, all recipients are accepted even if they are not in AD.

I've also added directly some users in the list box, but nothing to do : all recipients are allowed...

Need help, my server receive at leat 90% of junk email on wrong adress and send NDR...


Question by:FredTachet
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LVL 17

Expert Comment

ID: 11771653
By default Exchange won't process the recipient until after it has received the message as long as the domain part is valid per the recipient policy(s).

If you enable recipient filtering and check "Filter recipients who are not in the directory" then you will get 550's for invalid local recipients.
This will eliminate the need for your system to generate NDR's for messages that are sent to non-existent users. Which in the case of spammers, the sender is either an invalid destination (NDR gets stuck in retry until the message times out) or an invalid user. Both of these case caues the NDR to be dumped in the badmail directory, thus making it difficult to keep track of real badmail issues.

On the other side of the coin, it makes it easier for a remote party to perform a directory harvest attack. Please note the word easier, as some people are under the false assumption that DHA's can't happen if you don't have recipient filtering. DHA's can happen without recipient filtering by processing NDR's and removing the recipients from the spamlist.

Author Comment

ID: 11772015
>> If you enable recipient filtering and check "Filter recipients who are not in the directory" then you will get 550's for invalid local recipients.
That's what I want. Never mind for DHA now...
The problem is that we have a lot of customers that are not well protected against viruses, and that's why we receice a lot of junk or viruses emails.

Our spam and virus scan engine clean every of them, but this morning we have recevied 11 legitimate emails, 83 junk emails,  and 642 unknown user mail...

The strange thing is that I've already done it on an other exchange 2003 server as it's explain on the word documentation from MS and it's working fine, but I can figure out why it doesn't work for this server. The only difference I can see is That this one is an upgrade from EXC2000 and the other is a fresh install.


LVL 17

Accepted Solution

Microtech earned 250 total points
ID: 11773230
"Recipient filter rules apply only to anonymous connections. Authenticated users and Exchange servers bypass these validations". ref the doc you put a link to.
make sure no one is relaying

also look at this doc see if it helps http://support.microsoft.com/default.aspx?scid=KB;EN-US;823866


Author Comment

ID: 11773623
A friend of mine tell me to try to repair my installation, because sometimes there is problem with upgrade...

That's what I've done, and all is working fine now...

The repair has removed a connector used to fight relay in EXC2000, it's perhaps this connector that cause the problem.

Anyway thank for your time Microtech.

Topic is closed.
LVL 17

Expert Comment

ID: 11773912
Glad I could help a bit... if you feel I am deserving of the points the accept one of my comments

or if you wish to close then post a please close this question link in community support http://www.experts-exchange.com/Community_Support/

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