[dns-operations] about list's MX

[hua peng]

Are you sure? I meant the list adddress, not the mailbox of the domain 
itself.

> Dig this:
> ## dig dns-oarc.net MX
>
> ; <<>> DiG 9.8.3-P1 <<>> dns-oarc.net MX
> ;; global options: +cmd
> ;; Got answer:
> ;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 57215
> ;; flags: qr rd ra; QUERY: 1, ANSWER: 1, AUTHORITY: 0, ADDITIONAL: 0
>
> ;; QUESTION SECTION:
> ;dns-oarc.net.			IN	MX
>
> ;; ANSWER SECTION:
> dns-oarc.net.		30	IN	MX	0 mail.dns-oarc.net.
>
>
> ## dig  openstack.org MX
>
> ; <<>> DiG 9.8.3-P1 <<>> openstack.org MX
> ;; global options: +cmd
> ;; Got answer:
> ;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 1614
> ;; flags: qr rd ra; QUERY: 1, ANSWER: 2, AUTHORITY: 0, ADDITIONAL: 0
>
> ;; QUESTION SECTION:
> ;openstack.org.			IN	MX
>
> ;; ANSWER SECTION:
> openstack.org.		3600	IN	MX	10 mx1.emailsrvr.com.
> openstack.org.		3600	IN	MX	20 mx2.emailsrvr.com.
>
>
> Not this: