You can do:
this-machine in A
this_machine in CNAME
_ are allowable in CNAMEs because the RFC doesn't consider them "hostnames",
but in the end getting rid of the _ all together is probably the best

On Sun, Aug 24, 2008 at 11:18 PM, PM Wong wrote:

> We've been using the older version (pre 9.3)
> and the underscore in the hostname in A recored
> like
> this_machine IN A
> is okay.
> We have to upgrade the bind to 9.5
> The new version does not like underscore in the hostname
> Is there any way to workaround ?
> (otherwise we have to re-publish the web site URL
> with a new one
> as the user has used the underscore in its web site
> for quite some time)

-Ben Croswell