MX Records (Mail Exchange) are DNS records that are used to route email to email servers. You can have numerous MX Records posting to different email servers to prevent loss of email due to downtime. Email is sent to servers pointed to in MX records based on Priority which states that the lowest the Priority number the higher the priority of the server. Emails will be routed to MX records of 0 first.
Subdomains are prefixes to domain names that allow administrators to provide different web services to users, but do so using the same namespace so that it is easier to remember. Such as MAIL.failednormal.com, WWW.failednormal.com, VPN.failednormal.com… […]