Just a quick note: it's not a BCP yet, but it's also considered /extremely/ friendly by mail admins and others, if you use a naming convention for your rDNS that is easily placed into access.db and other "right-anchored" string matching mechanisms. e.g., if you have a dynamically assigned DSL range, and want to assign rDNS to it based on the IP,

123-45-67-89.dsl.dyn.example.net

is a lot easier to block via rudimentary mechanisms than

dsl-dyn-123-45-67-89.example.net

The bulkzone program will easily create right-anchored forward and reverse zonefiles for any size network block. http://backpan.cpan.org/authors/id/C/CH/CHRISJ/bulkzone.pl Just run it twice, and you've got it covered. On the bigger question of "charging" for reverse DNS: I would consider it part of the initial setup, or a deferred process tied to the initial setup. But if a customer swamps you with changes or updates beyond a reasonable amount, I'd consider delegating the reverse zone, or charging based on the number of changes. Just my 2 cents.