[exim] data acl

I have put

deny    message = Messages with embedded images are not allowed\
        \n ONLY by prior arrangement! \
        \n Send plaintext message first to arrange.
          !sender_domains = /usr/local/etc/exim/exim.whitelist
          condition = ${if match{$mime_content_type}{^image/}}
          condition = ${if def:mime_content_id}

in my data acl in an attempt to block all inserted image spam. But it is ignored have I put it in the wrong place or is it not right.
I got it or an example of it from the list.
Thanks