[exim] Detect missing reverse dns

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Author: Todd Lyons
Date:  
To: exim-users
Subject: [exim] Detect missing reverse dns
I want to work on a greylist solution that uses memcache for the
backend. I'm either going to use a single memcache server using the
method posted in this mailing list a couple months back, or I'm going
to use embedded perl so that it will spread it out over all memcache
servers. I have decided that for now I'm only going to greylist those
connections where the ip doesn't reverse resolve. From my limited
understanding, the hosts line below should only pass when there is an
actual PTR record for the IP address. But I get the log_message for
every hosts that connects, with or without reverse dns. What's wrong
with what I have below?

  warn    !senders       = :
          !authenticated = *
          !hosts         = +relay_from_hosts
          !hosts         = ${lookup dnsdb{ptr=$sender_host_address}{$value}fail}
          log_message    = No reverse DNS for $sender_host_address,
would greylist check


-- 
Regards...      Todd