Smart webmasters will NOT put their website DNS on the server because if the server goes down, DNS goes down, which usually includes email. A better option is to use your registrar’s DNS. This way, if your server goes down, your email and any other custom DNS specifications are still accessible to the Internet, meaning that your email will still work.
This assumes that you are not hosting your email on the same server as your website, which most smart webmasters already know. For example, if your using Google Apps for email, this video applies to you!