North American Network Operators Group Date Prev | Date Next | Date Index | Thread Index | Author Index | Historical Re: Underscores in host names
In article <[email protected]> you write: >Hello all. >We have a client containing an underscore in the email address domain >name. Our email server rejects it because of it's violation of the RFC >standard. This individuals claim is that he doesn't have problems >anywhere else and if this is going to be a problem he's "going to take >his business elsewhere"! > >I understand it's a violation of the standard, but does it pose a >security hole to the email server to allow this sort of mail? > >Thanks > RFC 952 and RFC 1123 describe what is currently legal in hostnames. Underscore is NOT a legal character in a hostname. Before anyone says that domain names allow underscore which they do. RFC 1034 Section 3.3 For hosts, the mapping depends on the existing syntax for host names which is a subset of the usual text representation for domain names, together with RR formats for describing host addresses, etc. Because we need a reliable inverse mapping from address to host name, a special mapping for addresses into the IN-ADDR.ARPA domain is also defined. Mail domains follow the same rules as for hostnames. RFC 821 and its replacement RFC 2821 havn't extended the syntax to include underscores. Mark
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