The domain-specific part of the SML DNS zone (e.g., ‘mydomain’ for mydomain.sml.dns.zone or leave empty for sml.dns.zone). Note: informative value.
SML domain should be up to 63 characters long, should only contain alphanumeric and hyphen characters,
should not start with a digit nor a hyphen and should not end with a hyphen.
The SML subdomain is already defined!
Domain with empty sml subdomain already exists!