[80893] in North American Network Operators' Group
Re: Underscores in host names
daemon@ATHENA.MIT.EDU (Jay R. Ashworth)
Tue May 17 22:50:32 2005
Date: Tue, 17 May 2005 22:46:59 -0400
From: "Jay R. Ashworth" <jra@baylink.com>
To: nanog@merit.edu
In-Reply-To: <200505180108.j4I1838V099518@drugs.dv.isc.org>; from Mark Andrews <Mark_Andrews@isc.org> on Wed, May 18, 2005 at 11:08:03AM +1000
Errors-To: owner-nanog@merit.edu
On Wed, May 18, 2005 at 11:08:03AM +1000, Mark Andrews wrote:
> In article <1116377042.592906.137650@g44g2000cwa.googlegroups.com> 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 jra@baylink.com
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
