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List:       bsdi-users
Subject:    Re: Spam Filter
From:       ronny () tmx ! com ! au (Ronny Cook)
Date:       2000-04-28 4:23:37
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> Date: Fri, 21 Apr 2000 09:40:32 -0400 (EDT)
> From: Shain Miley <shain@fingers.mkl.com>
> Subject: Spam Filter
> 
> Hi, I was wondering how I can stop mail to user@somedomain.com from being
> delivered to user@mydomain.com.  From what I understand spammers use the
> /etc/passwd file to extract a list of usernames and then the message that
> was not sent to any of my users get sent to them.  I am not sure if I have
> this right or not but I have gotten several messages from people who are
> getting messages in their mailbox and the to filed does not have their
> email address listed as the recipiant.  I am looking for a sendmail
> rule set or a filter of some sort.  Thanks.
> Shain

The short answer is Don't Do That. It's normal for the To: recipient to not
be the actual recipient. Three examples of when this can happen:
	- Mailing lists. You don't see your own email address listed in
	  the To: line of bsdi-users, do you?
	- Blind Carbon Copies (Bcc:) -- by design.
	- Email forwarded from another address, via a .forward or alias.
Then of course there are Cc:s, but that's really a variation on To:.

None of these are emails you want to block.

If you really, *really* want to do this, you may get some luck from trying
variations on the sendmail modifications that were introduced to block
Melissa. Failing that, look at procmail; it can be set up on a per-user
basis for those users who want this done.

		...Ronny
--
      Ronald Cook, UNIX Systems Engineer - TMX - an Asia Online company
 Email: ronny@asiaonline.net - Phone: +61-2-9230-7956 - Fax: +61-2-9519-2551

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