Date: Fri, 06 Apr 2007 10:43:38 -0400 From: Chuck Swiger <cswiger@mac.com> To: Christopher Martin <outsidefactor@iinet.net.au> Cc: freebsd-questions@freebsd.org Subject: Re: Receiver (To/CC envelope fields) addresses verification against LDAP/Active Directory in sendmail Message-ID: <46165C9A.7040906@mac.com> In-Reply-To: <05df01c7783b$a0dd74e0$d315a8c0@SAURON> References: <05df01c7783b$a0dd74e0$d315a8c0@SAURON>
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Christopher Martin wrote: > Spam with randomly generated recipient addresses is draining our mail > system's life away, and it seems the easiest way would be to verify the > receiving party's/parties' address against Active Directory and then > TEMPFAIL any mails that don't have any valid internal mails (rejects would > allow directory harvesting to work). > > Our network has a frontline mail filter system running FreeBSD 6.2, > Sendmail, milter-regex, Spam Assassin 3.1.8 and Clam AV, which delivers to > our internal Exchange server via a smarthost entry. You don't seem to mention using greylisting-- that will return a 4xx temp failure for all initial connections (except from sites which have been whitelisted). Only if the sender retries will the mail go through-- this works great against dictionary-style attacks. -- -Chuck
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