[exim] host IP whitelist

Hi all,

My intent is to employ a whitelist of trusted host IPs.

I am trying to employ an example straight from the current (4.89) exim
manual, without success.

The specific example that seems to not work as intended is from the
description of match_ip in Chapter 11. Namely:

       ${if match_ip{$sender_host_address}{iplsearch;/some/file}...

I have tried the following in the mail acl:
   accept logwrite = some text
   condition = ${if match_ip{$sender_host_address} \
                            {iplsearch;/path/to/whitelist.hosts}}

Where: whitelist.hosts contains exactly one line, containing a single
simple IP4 address, ala:
12.34.56.78: some descriptive text

The result of this code is to accept EVERY host that connects. (As 
indicated by the message written to the main log. Basically any random 
IP satisfies the match_ip condition. I hope someone can describe which 
part of the condition I have misread in the manual:
    a) match_ip
    b) iplsearch
    c) the file contents

--
Phil Carroll