On Fri, 16 Apr 2004, Jeff Chan wrote:
Does anyone have any more info on what characters are legal in domain names?
Domain names that are used as host names (i.e. most of them) must follow the preferred name syntax in section 2.3.1 of RFC 1035 (same as specified in RFC 952) with the relaxation specified in RFC 1123 that name components may start with a digit (e.g. 3com.com).
However the DNS itself doesn't have any such restriction, and a domain name that isn't a hostname may contain any character at all. See RFC2317 for an example of using / in a domain name. Note also the DNS zone master file format in section 5 of RFC 1035 which specifies how backslash escaping can be used to place unusual characters in domain names, for example a dot embedded in a label (rather than separating them as is usual).