Re: [cobalt-users] RAQ3: Catch-all email address

[Jeff Lasman <jblists@xxxxxxxxxxxxx>]

Dave Navarro wrote:

> At 11/1/2000, you wrote:
> >Dave Navarro wrote:
> >
> > > The DNS settings on the RAQ are as they are supposed to be (no CNAME).  I
> > > figured as long as the I had the DNS setup properly on the RAQ and the
> > > machine is using it's own DNS for internal lookups that I could then do
> > > whatever I like elsewhere (it works fine that way for all the domains I'm
> > > hosting on other machines).
> > >
> > > Am I kidding myself?
> >
> >Yes.  Do DNS right.  Or let someone do it who knows how to do it right.
> 
> I know how to do DNS.  And it's worked for me for YEARS on every other
> platform.
> 
> Damn, you're a very insulting person, aren't you.

I don't mean to be.
> Were you not breast fed as a child?

I have no idea.  My mother died when I was 3-1/2, and I never asked my
father.

However, I don't see what that has to do with the fact that you
solicited comments, and I commented.  I can certainly understand you
objecting to my comment.  But it still seems to me that you asked if it
was okay to do as you wrote "whatever I like".  I pointed out, perhaps
too abrasively for your taste (and if so, then I do apologize for that),
that just because it wasn't public, that didn't mean it still shouldn't
be done "right".

That's my only point, and while I apologize for pointing it abrasively,
I still stick to it.

What's "right" for you might really confuse the next person to take the
job.

The purpose of a CNAME is to point to a record you have no control over.

For example:  My dialup clients dial into the net through a third-party
telephone-access wholesaler I contract with.  To keep control over email
(and to get a handle on spam originating from their dialup blocks), they
block all port 25 transit through their dialups except through their own
mailservers.  Which are on round-robin DNS under the name
smtp.popsite.net.

I want my customers to send outgoing email through
"smtp.ez-access.com".  I could use an A record to point to a specific
IP, but it's not a good idea, since they (Megapop) could change the IP#
of the server at any time without telling me.  So I use a CNAME record,
pointing smtp.ez-access.com at smtp.popsite.net.

Why, some would ask, shouldn't I use a CNAME anyway?  Mainly because
CNAME records always require two lookups, putting more traffic on the
network, and more load on the DNS servers.  I still maintain that one
should only use them when necessary.

Many of the oldest "rules" surrounding DNS make no sense anymore in our
new world of virtual hosts; that's one reason I'm working on the new DNS
book.

There's also a reason why an MX record should never point to a host
named by a CNAME record; let's look at O'Reilly's "DNS and Bind":

Page 97:
"One caveat: most mailers will only look for their local host's
canonical domain name in the list of MX records. They don't check for
aliases (domain names on the left side of CNAME records). Unless you
always use canonical names in your MX records, there's no guarantee a
mailer will be able to find itself in the MX list, and you'll run the
risk of having your mail loop."

A little additional reading will show that a CNAME record is used to
point an "alias" to a canonical name, and an A record (or address)
record is used to show the address of a host.

I hope this has been helpful, and not insulting.

Jeff
-- 
Jeff Lasman <jblists@xxxxxxxxxxxxx>
nobaloney.net
P. O. Box 52672
Riverside, CA  92517
voice: (909) 787-8589  *  fax: (909) 782-0205