[exim] Trapping Connection Errors

Third attempt to post to the mailing list !
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Exim 4.63 (Centos 5) and Exim 4.72 (Centos 6).

I would like to trap and then use the absence of a Host name in ACL
Connection.

Exim log shows: 13:35:34 no host name found for IP address 207.191.2.243

The best I have managed to do is:-

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warn  message   = ${run{SHELL -c "PHP EXIM_ALERT \
                  'cA:host' \
                  'host$sender_host_name' \
                  'ip$sender_host_address' \
                  'mx${primary_hostname}' \
                  'msg[SNA04] (Host name absent) or (No Reverse DNS)' \
                  'port$sender_host_port'"}}
      condition = ${if and{{def:sender_host_address} \
                   {!def:sender_host_name}} {yes}{no}}

deny  message   = [SNA04] Rejected. (Host name absent) or (No Reverse \
                   DNS) ...........
      condition = ${if and{{def:sender_host_address} \
                   {!def:sender_host_name}} {yes}{no}}
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The above condition, found on the Internet, can not discriminate between
the absence of a host name and the absence of a Reverse DNS entry.

I have tried to use, without success, various permutations including

condition = ${if eq{ {$sender_host_name}{} {yes}{no} }
condition = ${if match{ {$sender_host_name}{} {yes}{no} }

All suggestions appreciated.

Thank you.

Paul.