Description of DNSBLs

This draft is now standards track, in IETF Last Call.

Primary author is John Levine, document shepherd is Alexey Melnikov.

The latest version is here.

The current version is redone to be standards track rather than informational, so it now contains MUST and SHOULD and other normative language to describe the proper technical operation (which is NOT, repeat NOT, related to the listing or delisting policy) of a DNSBL.