Bogus

go to DNS forwarder page and try to add a new host, for example my_host.mydomain.com. the UI does not allow hostnames containing "_".

RFCs mandate that a hostname's labels may contain only the ASCII letters 'a' through 'z' (case-insensitive), the digits '0' through '9', and the hyphen. Hostname labels cannot begin or end with a hyphen. No other symbols, punctuation characters, or blank spaces are permitted.