using cname for redirection?

[aklist_bind at enigmedia.com]

Thank you Bill and Barry.

I wasn't sure if GoDaddy used a CNAME, or just pointed 
"webmail.<godaddycustomerdomain>.com" to the same IP address as 
"email.secureserver.net".

Either way, anyone using "webmail.mydomain.com" is redirected to the 
secureserver.net site, and their own domain is appended in a query string 
and pre-supplied as the mailserver login...or you can manually enter it, so 
my redirection in this case doesn't cause problems. The MX records for the 
domain are secureserver.net records in either case.

I've only used CNAMES to alias multiple names to the same IP within the 
domain, like aliasing ftp.domain.com to www.domain.com...I wasn't sure if 
you could actually point to a different domain with a CNAME...thanks for 
that clarification.

It looks like godaddy is only using a single IP address for 
"email.secureserver.net"...but obviously it would be better to use a CNAME 
in case they change the IP.

Thanks again.

----- Original Message ----- 
From: "Bill Larson" <wllarso at swcp.com>
To: <aklist_bind at enigmedia.comaklist_bind@enigmedia.com>
Cc: <bind-users at isc.org>
Sent: Saturday, December 29, 2007 4:28 PM
Subject: Re: using cname for redirection?


> On Dec 29, 2007, at 1:11 PM, <aklist_bind at enigmedia.com> 
> <aklist_bind at enigmedia.com> wrote:
>
>> Hi All: Is there any valid way in DNS to point requests for
>> "something.domain1.com" to "somethingelse.domain2.com"?
>>
>> Can a CNAME be used for that?
>
> Isn't this exactly the point of a CNAME?  Just because the target  doesn't 
> belong in the same zone doesn't matter.
>
>> In this particular instance, I have a domain where the mail is  being 
>> hosted
>> at godaddy.com (email.secureserver.net), and when godaddy  maintained the 
>> NS,
>> they were aliasing "webmail.yourdomain.com" to  "email.secureserver.net".
>>
>> If I take over the DNS, normally I'd need to create an A record for
>> "webmail" and point it at the IP for "email.secureserver.net"...but  what 
>> if
>> there is more than one IP for that address?
>
> This is an issue for the email server configuration rather than just  DNS. 
> The email server has to recognize the name(s) for the domains  that it is 
> serving mail for.  When they create a CNAME record for 
> "webmail.yourdomain.com" that resolves to "email.secureserver.net", 
> unless they have also configured their mail server to accept mail 
> addressed to "webmail.yourdomain.com" (and very likely  "yourdomain.com") 
> this mail will be bounced when it is sent there.
>
> This email configuration isn't necessarily controlled by DNS.   Imagine if 
> it were, then I were simply identify that my mail, when  addressed as 
> USER at example.com, and example.com were to point to  207.158.46.202, the IP 
> address for enigmedia.com, then should I  expect that this mail would be 
> accepted by your server?   Emphatically, NO!  It would bounce because this 
> server isn't  configured to accept mail addressed to "example.com".
>
> You need to coordinate the effort of "taking over the DNS" with the 
> organizations involved.  Obviously, this is you or whomever you are  using 
> for DNS services, but this will also include your registrar to  insure 
> that the parent registration can be changed, your current DNS  hosting 
> service to insure that the old DNS information is removed,  and your email 
> hosting service to insure that they will still  function.  At the same 
> time, you will need to insure that you have a  properly operating DNS 
> service that fulfills the recommendations of  RFC2182/BCP16, "Selection 
> and Operation of Secondary DNS Servers".
>
> Bill Larson