From owner-freebsd-isp Sun May 11 15:55:35 1997 Return-Path: Received: (from root@localhost) by hub.freebsd.org (8.8.5/8.8.5) id PAA16985 for isp-outgoing; Sun, 11 May 1997 15:55:35 -0700 (PDT) Received: from wopr.inetu.net ([207.18.13.3]) by hub.freebsd.org (8.8.5/8.8.5) with ESMTP id PAA16980 for ; Sun, 11 May 1997 15:55:33 -0700 (PDT) Received: from localhost (dev@localhost) by wopr.inetu.net (8.8.5/8.8.5) with SMTP id TAA22039 for ; Sun, 11 May 1997 19:00:45 -0400 (EDT) Date: Sun, 11 May 1997 19:00:45 -0400 (EDT) From: Dev Chanchani To: freebsd-isp@freebsd.org Subject: Sendmail hack Message-ID: MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: owner-isp@freebsd.org X-Loop: FreeBSD.org Precedence: bulk I and my users have been receiving a lot of spam mail recently. Usually, this is not so bad because I will just reply to remove me. However, more and more spammers are using fake domain names to send their spam from. I was wondering if you could hack sendmail to do a lookup on the reply to or from address. If the domain name is non-existant, reject the mail. For example: mail coming from: joe@schmoe.com would be accepted because the domain name exists (need not really resolve it). mail coming from: joe@non-existant.com would be rejected because non-existant.com is not in the whois database. Anyone have any ideas?