[dns-operations] Can MX be working with CNAME?

[Mukund Sivaraman]

Hi Doug

On Fri, Oct 18, 2013 at 04:46:06PM +0800, Doug wrote:
> Hello,
> 
> $ idig plus.google.com mx
> plus.google.com.    1200    IN    CNAME    plus-china.l.google.com.
> plus-china.l.google.com. 600    IN    MX    40 alt3.aspmx.l.google.com.
> plus-china.l.google.com. 600    IN    MX    50 alt4.aspmx.l.google.com.
> plus-china.l.google.com. 600    IN    MX    10 aspmx.l.google.com.
> plus-china.l.google.com. 600    IN    MX    20 alt1.aspmx.l.google.com.
> plus-china.l.google.com. 600    IN    MX    30 alt2.aspmx.l.google.com.
> 
> I never saw this type of MX.  Are they valid records?

I don't get a CNAME result here (in India), but this is quite similar to
what RFC 2317 (Classless IN-ADDR.ARPA delegation) does with CNAME for
PTR type. Here is an example:

dig -x 149.20.53.1

(Note that RFC 2317 is a "best practice" only, i.e., it does not require
any extra protocol support.)

		Mukund
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