“This article covers setting up BIND v8 with proper ACLs,
some POP3/IMAP solutions, and has an example “feature-complete”
rc.firewall script.”
“BIND v8 adds important security functionality over BIND v4
(although it is arguably more “feature ridden” compared to the
older code) in the form of ACLs. ACL stands for Access Control
List, and is a mechanism for implementation fairly atomic control
over your rules. (Note: I will not discuss setting up a BIND server
in the basic sense, as it is covered better elsewhere.)”