Re: Exim not accepting undescore in server name?
On Tue, Jan 17, 2006 at 10:54:30AM +0000, Andy Smith wrote:
> On Tue, Jan 17, 2006 at 02:14:44AM -0700, Michael Loftis wrote:
> > The unfortunate reality is that because the DNS implementations have never
> > expressly forbidden _'s we have to allow sending and receiving to/from
> > hostnames with _'s.
that's because in the early years, underscores WERE permitted in domain
names.
that changed somewhere around 1993 or 1994, IIRC.
> Why should DNS dictate what is acceptable for email? DNS is designed
> to be more general than email, or web, or even IP.
it doesn't. DNS dictates what is acceptable in a domain name. the fact that
email is usually sent to a domain name is incidental.
> Underscores are not acceptable in internet hostnames as per STD13
> and RFC1035. If people choose to do this they will experience
> breakage all over, from stricter OS resolver libraries, to
> application proxies (squid!). Giving in to their wishes in this
> regard does not ultimately help them, it's a rocket launcher with
> foot-seeking missiles.
yep. in short, don't use underscores in domain names.
bind (and some other DNS programs) support underscores for legacy
reasons only, basically to give people time to rename any hosts with
now-bogus names. they probably should have stopped doing that a few
years ago.
craig
--
craig sanders <cas@taz.net.au> (part time cyborg)
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