If you go to $foo.branchable.com, for example to check if it exists, and then create it, the NXDOMAIN is cached. Could be a problem later. Is there a DNS TTL adjustment that can amelorate this? Should we have a wildcard entry to avoid NXDOMAIN? (we could then redirect from the wildcarded host to the actual server to deal with cached dns)

fixed; setting the SOA minimum to 0 fixes this by avoiding NXDOMAIN caching, at the expense of some server load.

(Still seeing NXDOMAIN be cached, but for just a few minutes at least in testing. --Joey)