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North American Network Operators Group Date Prev | Date Next | Date Index | Thread Index | Author Index | Historical Re: Underscores in host names
On Wed, May 18, 2005 at 11:08:03AM +1000, Mark Andrews wrote: > 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? > > 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. Those with long memories will remember when Apple got strict on this years ago, and lots of websites became unreachable to their users... Cheers, -- jra -- Jay R. Ashworth [email protected] Designer Baylink RFC 2100 Ashworth & Associates The Things I Think '87 e24 St Petersburg FL USA http://baylink.pitas.com +1 727 647 1274 If you can read this... thank a system administrator. Or two. --me
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