mail confusion

[Derek Martin]

On Thu, Nov 03, 2005 at 07:27:19AM +1030, Tim wrote:
> > I'm not sure what you're trying to say here.  My reading of the RFC
> > agrees with what I wrote above.  If your point was something
> > different, then I guess I'll have to ask you to clarify...
> 
> It doesn't explicitly say that localhost means 127.0.0.1, it says that
> it's a top level domain name.  Commonly used for that purpose, and might
> not work well for other uses (actually used as a top level domain name),
> but it is one.

OK... you're certainly able to use it that way if you like.  It WILL
work fine, if you set up your internal DNS server to be authoritative
for the "localhost." zone (or use hosts files, or NIS, or ...), but
honestly I still don't see the need.

> >> What is needed is a reserved domain name for local hosting of servers,
> 
> > Why?  If the hosts are on a network which is connected to the
> > Internet, they'll have their own domain already.  If they're not, then
> > no domain is needed.  Or, if for the convenience of managing your
> > network, having domains makes sense, then you should register a domain
> > name anyway, even if you're not going to use it on the Internet.  That
> > way, if a time comes when you WANT to connect those systems to the
> > 'Net, you don't need to reconfigure them all.
> 
> A simple reason is the sheer number of LANs with an internet connection
> where some bozo has taken someone else's domain named and used it
> themselves, then misuses in public, too.

Well, there are idiots everywhere.  Those idiots would do just as well
with their own genuine domain name as they would with some reserved
one.  Better, since as you say, they're actually using it on the
Internet.

I think the problem is that idiots are idiots!  It's not that we need
another reserved TLD for this...  Idiots don't tend to mind the
standards anyway, largely because they're not aware of them in the
first place... ;-)

> Not to mention the problems they'll have with their own network when
> something resolves to an outside address.

Right.  So it's better if they use a real domain...  But as you say,
there are several domains already reserved, so they can just use one
of those.  Or, just don't use one at all, and stop doing stupid
things.  ;-)

> > I can't speak for all mail server software, but I'm pretty sure
> > sendmail doesn't require an FQDN.  
>
> I seem to recall that if you do try using user at fakename sort of address,
> it'll try appending something to make a FQDN [...] 

Sure, it does that if you tell it to, and by default (since most
people want to send e-mail on the public Internet) it's usually
configured that way.  But it doesn't need to be...  You can tell it
not to do that.

> [...] presuming that anything without a dot is just an alias.

...though I'm not sure that it's making any such presumption.  The
usual reason to do this is because once mail from such a system hits
the public internet, it's going to be hard to respond to if there's no
FQDN in the headers.  But still, sendmail has no trouble sending mail
to unqualified hosts, so long as it can somehow resolve the
unqualified name to an IP (usually via /etc/hosts or NIS, rather than
DNS of course).

> > The only server which SHOULD require a FQDN is the DNS server, for
> > (hopefully) obvious reasons.  :)  But even then, "myhost" can be a
> > top-level domain and have its own A record.  That's just not a very
> > useful way to manage DNS.  Still, possible.
> 
> Making up names leads to the problem I brought up.  If you just invent
> something, it can clash with something else.  Now, or later.

So... register a domain name.  :)  If you don't need one, don't use
one at all.  If you're going to send e-mail from your host without
relaying through your ISP's mail server, or if you're going to run a
server on your machine, then obviously you need one, and it MUST be
legitimate.  Otherwise, there's no reason why you should...  Thusfar,
I don't think you've provided any substantial reason why for a
stand-alone network, one is required.  And I assert that you will not
find one.  Though I've been wrong before...  ;-)

It's been quite a while since I've tried to run my own system without
a FQDN, so I don't remember the details, but IIRC the only time I've
ever encountered a problem with not having a FQDN was with some (IMO)
brain-dead, red-hat-specific software that was hard-coded to look for
localhost.localdomain for some unknown reason.  Normally when I
install systems, whether my own or production servers, I remove the
localhost.localdomain from the hosts file, and never have any
problems.  But Red Hat seems to like this convention for some reason,
so you have to make sure all your software is not configured to use
it.  My normal solution to that problem is just not to use their
system management software. ;-)

-- 
Derek D. Martin
http://www.pizzashack.org/
GPG Key ID: 0x81CFE75D

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