Proper ACL condition to block failed rDNS lookup

AC via Exim-users <[email protected]>
Newsgroups gmane.mail.exim.user
Message-ID <[email protected]>
I want to block any connection that doesn't have a successful rDNS (logs 
report "no host name found") but searching around results in so many 
different variants of an ACL rule to do this.

What is the proper way (likely in acl_smtp_connect if I'm not mistaken) 
that will simply reject any conection that comes from a bare IP with no 
rDNS? Note I'm not asking that I block something where the incoming 
hostname doesn't match the rDNS where the two might mismatch (such as an 
MX record vs. a more general domain), I'm only looking to block anything 
that has absolutely no rDNS value so I don't want to use the 
"reverse_host_lookup" option.

The closest thing I found was in the mailing list from 2008:

defer
  !condition = ${lookup dnsdb{defer_never,ptr=$sender_host_address}{yes}}
  message    = Reverse DNS lookup failed for host $sender_host_address



Is this still a correct suggestion?

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