+JH/19 SPF: change the Authentication-Results expansion component to give
+ smtp.helo when the sender domain is empty. Previously it gave
+ "smtp.mailfrom=<>"
+
+JH/20 Bug 2631: ACL dnslist conditions now ignore and log any lookups returns
+ not in 127.0.0.0/8 to help in spotting list domains taken over by a
+ domain-parking registrar.
+