Underscores in Host Names

[Mark Andrews]

> R.D. wrote:
> 
> >Hello all.
> >We have a client containing an underscore in the email address domain
> >name.  
> >
> Please define exactly what you mean by that. Do you mean the *owner* of 
> the MX record has an underscore in it, or do you mean that the MX 
> *target* has an underscore in it? The target shouldn't have an 
> underscore in it, since it is considered to be a "hostname" and 
> underscores in "hostname"s is forbidden by RFC 952. If it's the MX 
> *owner* that has an underscore in it, then I think that's allowable 
> under the standards, and your email software is being too picky.

	The owner of a MX record is also restricted.  See RFC 2821.
                                                                          
--
Mark Andrews, ISC
1 Seymour St., Dundas Valley, NSW 2117, Australia
PHONE: +61 2 9871 4742                 INTERNET: Mark_Andrews at isc.org