I added a subdomain to a zone file and when I reloaded named I noticed the following error in messages:
Oct 29 09:31:06 master named[28254]: tabordesignbuild.com.db:59: beta_live.sampledomain.com: bad owner name (check-names)
Oct 29 09:31:06 master named[28254]: zone sampledomain.com/IN: loading from master file sampledomain.com.db failed: bad owner name (check-names)
We are running BIND 9 and after doing a little searching it turns out that with the default configuration for BIND 9 underscores are now verbotten.
Evidently, if you need to include an underscore “_” in your domain name you can turn off name-checking but that seems to be overwhelmingly not recommended by the wider sysadmin community.