exim4 & CHECK_RCPT_LOCAL_ACL_FILE

I am running a ubuntu server (I got convinced and there is not one day that I do not regret it!) which runs Exim. Deep within the split configuration's ACL files, I found this: # This hook allows you to hook in your own ACLs without having to # modify this file. If you do it like we suggest, you'll end up with # a small performance penalty since there is an additional file being # accessed. This doesn't happen if you leave the macro unset. .ifdef CHECK_RCPT_LOCAL_ACL_FILE .include CHECK_RCPT_LOCAL_ACL_FILE .endif A search CHECK_RCPT_LOCAL_ACL_FILE yields many such stanza but no where does it tell you *where to create the variable* or *what the file should look like*. The latter should be obvious as it will just contain some more ACL commands. However, the former is a mystery… Anyone got an idea? I did try to ask this on ask.ubuntu and as usual got nothing whatsoever… Note that the following stanza works just fine in the conf.d/acl/30_exim4-config_check_rcpt file but modifying system files like that will lead to trouble the next time Ubuntu decides to update… deny condition = ${lookup{$local_part}nwildlsearch{/etc/exim4/black.list}{yes}{no}} logwrite = :main,reject: $sender_host_address - $local_part@$domain is only used by spammers message = User is black listed. Go away.