Im seeing this in my logs;
2017-04-26 07:01:34 H=([103.47.66.214]) [103.47.66.214] Warning: ACL "warn" statement skipped: condition test deferred: failed to expand ACL string "${lookup dnsdb{ptr=$sender_host_address}{false}{true}}": lookup of "ptr=103.47.66.214" gave DEFER:
2017-04-26 07:01:34 H=([103.47.66.214]) [103.47.66.214] Warning: ACL "warn" statement skipped: condition test deferred: failed to expand ACL string "${lookup dnsdb{ptr=$sender_host_address}{false}{true}}": lookup of "ptr=103.47.66.214" gave DEFER: