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

[Joseph S D Yao]

On 2013-10-18 04:46, 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?
...


Doug,

This is fine.  What would be bad is having a CNAME associated with the 
other side:

mail.domain.ex.         MX      10 bad.mailer.ex.
bad.mailer.ex.          CNAME   real.mailer.ex.

Cf. RFC 1912, 2.4 CNAME records.


Joe Yao