Date: Sun, 11 May 1997 19:00:45 -0400 (EDT) From: Dev Chanchani <dev@wopr.inetu.net> To: freebsd-isp@freebsd.org Subject: Sendmail hack Message-ID: <Pine.BSF.3.95q.970511185824.21995A-100000@wopr.inetu.net>
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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?
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