Anchor is enforcing the RFC1034 rules on domain name labels which state that...
"The labels must follow the rules for ARPANET host names. They must
start with a letter, end with a letter or digit, and have as interior
characters only letters, digits, and hyphen. There are also some
restrictions on the length. Labels must be 63 characters or less."
However, the subsequent RFC2181 states that...
"The DNS itself places only one restriction on the particular labels
that can be used to identify resource records. That one restriction
relates to the length of the label and the full name. The length of
any one label is limited to between 1 and 63 octets. A full domain
name is limited to 255 octets (including the separators). The zero
length full name is defined as representing the root of the DNS tree,
and is typically written and displayed as ".". Those restrictions
aside, any binary string whatever can be used as the label of any
resource record."
Really the regex stored in anchor/util.py should be relaxed to not require a leading letter.
RE_DOMAIN_LABEL = re.compile("^[a-z](?:[-a-z0-9]*[a-z0-9])?$", re.IGNORECASE)
Thanks, I'll have a look at that.