[Mimedefang] Specifying valid users?

Kevin A. McGrail kmcgrail at pccc.com
Wed Aug 10 15:35:33 EDT 2005

I hesitate to answer this fully because I think the archives must be 
chock-full of answers to this question but I will give you the following 
pointers just because you seem a little out of your depth:

The spam pattern you are seeing is most likely what is called a dictionary 
attack.  Blocking these at the gateway is essential for any company as the 
bounces created by these attacks are as bad as the attacks themselves in 
many cases where they forge the from address.

For exchange 2003, see 
http://www.peregrinehw.com/downloads/ldap/NOTE-EXCHANGE2003 and setup a 
recipient filter using  md_check_against_smtp_server.

For exchange 2000, setup an LDAP link for sendmail.  I use this solution: 


> Hi all, I've noticed that lately a lot of spam is directed to people
> that don't actually exist in my company.  It looks like spammers are
> just guessing names of people who might work here.  Since my Linux box
> is just a relay for the exchange server I don't know of anyway to
> actually do checking to see if a user exists.  Also, since anything
> labeled as spam gets redirected to a specific mailbox it doesn't even
> get rejected at the exchange server.

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