[exim] mime ACL not working

i have this in the ACL section and exim still happily delivers
messages with .exe attachments.
What am I missing here?

acl_smtp_mime:

deny
   condition = ${if match {$mime_filename}\
     {\N\.(com|vbs|bat|pif|scr|exe)$\N}}
   message = no Windows executeables accepted here
   log_message = reject, ${substr_-4_4:$mime_filename} file