[SURBL-Discuss] Re: Fwd: Re: Fwd: Re: Announcing SURBL support in SA 2.63 and 3.0 plugins - bug ?

Tony Finch dot at dotat.at
Fri Apr 16 13:55:34 CEST 2004

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

Tony Finch  <dot at dotat.at>  http://dotat.at/

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