[dns-operations] domain has no MX record

[support at cloudwebdns.com]

I have found this list address has no MX record, lists.ceph.com
you can find their subscribe info at,

http://ceph.com/resources/mailing-list-irc/

So some email systems can not deliver messages to it, such as Aliyun's 
which returns,

(8)lists.ceph.com resolving by dns failed

I know the deliver agent should try A record if there is no MX exists.
But any way lacks MX for a public email domain is not good practical.

Is it? :p