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Check MX Record of Incoming Mail

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Check MX Record of Incoming Mail - 7.Feb.2008 6:22:45 PM

AdmiralNemo

Posts: 11
Joined: 14.Dec.2007
Status: offline

Hi All,

My server is receiving extremely large amounts of spam addressed to invalid users on my domain. As a result, Exchange generates an undeliverable message and sends it back to the sender, but unfortunately, many of the sender's addresses are invalid themselves. 60% of the spam I receive comes from silly addresses like "lkjgf@n". Clearly "n" is not a valid DNS domain so Exchange just sits there all day trying to contact the mail server for "n" to send this undeliverable to. After several hours, outbound queues get so clogged, I have to stop the services and clear them out.

My question to you is this: Is there a way for Exchange to evaluate the domain portion of sender addresses of incoming mail and ensure there is in fact an MX record associated with it? Or better yet, ensure that the message is coming *from* the designated MX record for that domain and if not, silently drop the connection? Forgive me for saying this, but Postfix has such features, and since I implemented them, my spam volume has been significantly reduced.

Any suggestions you have are very much appreciated.

Thanks

Post #: 1

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RE: Check MX Record of Incoming Mail - 8.Feb.2008 4:23:03 AM

alex.c

Posts: 47
Joined: 12.Jan.2005
From: AT/Vienna
Status: offline

Hi Admiral *salute*

I assume you are using Exchange 2003..?

First lets address "spam addressed to invalid users on my domain�.

You can filter mails which are addressed to invalid users going this way:

-open Exchange System Managerexpand Global Settings
-open the properties of Message deliveryin the "Recipient Filtering� tab, check "Filter recipients who are not in the directory� and click OK
-navigate to your server object and expand to Protocols � SMTP
-open the properties of your Default SMTP Virtual server
-In the General-tab click "Advanced�
-Mark the appropriate IP address and click EditCheck "Apply Recipient Filter� and click OK, OK, OK
-Restart the Default SMTP Virtual Server

Now your Exchanger does not accept messages to invalid recipients and drops the connection.

To be continued�